Brain Studies on Porn Users

Printer-friendly version

This page lists all the studies assessing the brain structure and functioning of Internet porn users. To date every study offers support for the porn addiction model (no studies falsify the porn addiction model). The results of these 37 neurological studies (and upcoming studies) are consistent with 260+ Internet addiction "brain studies", many of which also include internet porn use. All support the premise that internet porn use can cause addiction-related brain changes, as do 13 recent neuroscience-based reviews of the literature:

Reviews of the literature:

1) Neuroscience of Internet Pornography Addiction: A Review and Update (Love et al., 2015). A thorough review of the neuroscience literature related to Internet addiction sub-types, with special focus on internet porn addiction. The review also critiques two recent headline-grabbing EEG studies by teams headed by Prause (who claims the findings cast doubt on porn addiction). Excerpts:

Many recognize that several behaviors potentially affecting the reward circuitry in human brains lead to a loss of control and other symptoms of addiction in at least some individuals. Regarding Internet addiction, neuroscientific research supports the assumption that underlying neural processes are similar to substance addiction... Within this review, we give a summary of the concepts proposed underlying addiction and give an overview about neuroscientific studies on Internet addiction and Internet gaming disorder. Moreover, we reviewed available neuroscientific literature on Internet pornography addiction and connect the results to the addiction model. The review leads to the conclusion that Internet pornography addiction fits into the addiction framework and shares similar basic mechanisms with substance addiction.

2) Sex Addiction as a Disease: Evidence for Assessment, Diagnosis, and Response to Critics (Phillips et al., 2015), which provides a chart that takes on specific criticisms of porn/sex addiction, offering citations that counter them. Excerpts:

As seen throughout this article, the common criticisms of sex as a legitimate addiction do not hold up when compared to the movement within the clinical and scientific communities over the past few decades. There is ample scientific evidence and support for sex as well as other behaviors to be accepted as addiction. This support is coming from multiple fields of practice and offers incredible hope to truly embrace change as we better understand the problem. Decades of research and developments in the field of addiction medicine and neuroscience reveal the underlying brain mechanisms involved in addiction. Scientists have identified common pathways affected by addictive behavior as well as differences between the brains of addicted and non-addicted individuals, revealing common elements of addiction, regardless of the substance or behavior. However, there remains a gap between the scientific advances and the understanding by the general public, public policy, and treatment advances.

3) Cybersex Addiction (Brand & Laier, 2015). Excerpts:

Many individuals use cybersex applications, particularly Internet pornography. Some individuals experience a loss of control over their cybersex use and report that they cannot regulate their cybersex use even if they experienced negative consequences. In recent articles, cybersex addiction is considered a specific type of Internet addiction. Some current studies investigated parallels between cybersex addiction and other behavioral addictions, such as Internet Gaming Disorder. Cue-reactivity and craving are considered to play a major role in cybersex addiction. Also, neurocognitive mechanisms of development and maintenance of cybersex addiction primarily involve impairments in decision making and executive functions. Neuroimaging studies support the assumption of meaningful commonalities between cybersex addiction and other behavioral addictions as well as substance dependency.

4) Neurobiology of Compulsive Sexual Behavior: Emerging Science (Kraus et al., 2016). Excerpts:

Although not included in DSM-5, compulsive sexual behavior (CSB) can be diagnosed in ICD-10 as an impulse control disorder. However, debate exists about CSB’s classification. Additional research is needed to understand how neurobiological features relate to clinically relevant measures like treatment outcomes for CSB. Classifying CSB as a ‘behavioral addiction’ would have significant implications for policy, prevention and treatment efforts….. Given some similarities between CSB and drug addictions, interventions effective for addictions may hold promise for CSB, thus providing insight into future research directions to investigate this possibility directly.

5) Should Compulsive Sexual Behavior be Considered an Addiction? (Kraus et al., 2016). Excerpts:

With the release of DSM-5, gambling disorder was reclassified with substance use disorders. This change challenged beliefs that addiction occurred only by ingesting of mind-altering substances and has significant implications for policy, prevention and treatment strategies. Data suggest that excessive engagement in other behaviors (e.g. gaming, sex, compulsive shopping) may share clinical, genetic, neurobiological and phenomenological parallels with substance addictions.

Another area needing more research involves considering how technological changes may be influencing human sexual behaviors. Given that data suggest that sexual behaviors are facilitated through Internet and smartphone applications, additional research should consider how digital technologies relate to CSB (e.g. compulsive masturbation to Internet pornography or sex chatrooms) and engagement in risky sexual behaviors (e.g. condomless sex, multiple sexual partners on one occasion).

Overlapping features exist between CSB and substance use disorders. Common neurotransmitter systems may contribute to CSB and substance use disorders, and recent neuroimaging studies highlight similarities relating to craving and attentional biases. Similar pharmacological and psychotherapeutic treatments may be applicable to CSB and substance addictions.

6) Neurobiological Basis of Hypersexuality (Kuhn & Gallinat, 2016). Excerpts:

Behavioral addictions and in particular hypersexuality should remind us of the fact that addictive behavior actually relies on our natural survival system. Sex is an essential component in survival of species since it is the pathway for reproduction. Therefore it is extremely important that sex is considered pleasurable and has primal rewarding properties, and although it may turn into an addiction at which point sex may be pursued in a dangerous and counterproductive way, the neural basis for addiction might actually serve very important purposes in primal goal pursuit of individuals…. Taken together, the evidence seems to imply that alterations in the frontal lobe, amygdala, hippocampus, hypothalamus, septum, and brain regions that process reward play a prominent role in the emergence of hypersexuality. Genetic studies and neuropharmacological treatment approaches point at an involvement of the dopaminergic system.

7) Compulsive Sexual Behaviour as a Behavioural Addiction: The Impact of the Internet and Other Issues (Griffiths, 2016). Excerpts:

I have carried out empirical research into many different behavioural addictions (gambling, video-gaming, internet use, exercise, sex, work, etc.) and have argued that some types of problematic sexual behaviour can be classed as sex addiction, depending upon the definition of addiction used….

Whether problematic sexual behaviour is described as compulsive sexual behavior (CSB), sex addiction and/or hypersexual disorder, there are thousands of psychological therapists around the world who treat such disorders. Consequently, clinical evidence from those who help and treat such individuals should be given greater credence by the psychiatric community….

Arguably the most important development in the field of CSB and sex addiction is how the internet is changing and facilitating CSB. This was not mentioned until the concluding paragraph, yet research into online sex addiction (while comprising a small empirical base) has existed since the late 1990s, including sample sizes of up to almost 10 000 individuals. In fact, there have been recent reviews of empirical data concerning online sex addiction and treatment. These have outlined the many specific features of the internet that may facilitate and stimulate addictive tendencies in relation to sexual behaviour (accessibility, affordability, anonymity, convenience, escape, disinhibition, etc.).

8) Searching for Clarity in Muddy Water: Future Considerations for Classifying Compulsive Sexual Behavior as An Addiction (Kraus et al., 2016). Excerpts:

We recently considered evidence for classifying compulsive sexual behavior (CSB) as a non-substance (behavioral) addiction. Our review found that CSB shared clinical, neurobiological and phenomenological parallels with substance-use disorders….

Although the American Psychiatric Association rejected hypersexual disorder from DSM-5, a diagnosis of CSB (excessive sex drive) can be made using ICD-10. CSB is also being considered by ICD-11, although its ultimate inclusion is not certain. Future research should continue to build knowledge and strengthen a framework for better understanding CSB and translating this information into improved policy, prevention, diagnosis, and treatment efforts to minimize the negative impacts of CSB.

9) Is Internet Pornography Causing Sexual Dysfunctions? A Review With Clinical Reports (Park et al., 2016). An extensive review of the literature related to porn-induced sexual problems. Involving 7 US Navy doctors and Gary Wilson, the review provides the latest data revealing a tremendous rise in youthful sexual problems. It also reviews the neurological studies related to porn addiction and sexual conditioning via Internet porn. The doctors provide 3 clinical reports of men who developed porn-induced sexual dysfunctions. A second 2016 paper by Gary Wilson discusses the importance of studying the effects of porn by having subjects abstain from porn use: Eliminate Chronic Internet Pornography Use to Reveal Its Effects (2016).

10) Integrating Psychological and Neurobiological Considerations Regarding The Development and Maintenance of Specific Internet-Use Disorders: An Interaction of Person-Affect-Cognition-Execution model (Brand et al., 2016). A review of the mechanisms underlying the development and maintenance of specific Internet-use disorders, including "Internet-pornography-viewing disorder". The authors suggest that pornography addiction (and cybersex addiction) be classified as internet use disorders and placed with other behavioral addictions under substance-use disorders as addictive behaviors. Excerpts:

Although the DSM-5 focuses on Internet gaming, a meaningful number of authors indicate that treatment-seeking individuals may also use other Internet applications or sites addictively….

From the current state of research, we suggest to include Internet-use disorders in the upcoming ICD-11. It is important to note that beyond Internet-gaming disorder, other types of applications are also used problematically. One approach could involve the introduction of a general term of Internet-use disorder, which could then be specified considering the first-choice application that is used (for example Internet-gaming disorder, Internet-gambling disorder, Internet-pornography-use disorder, Internet-communication disorder, and Internet-shopping disorder).

11) The Neurobiology of Sexual Addiction: Chapter from Neurobiology of Addictions, Oxford Press (Hilton et al., 2016) - Excerpts:

We review the neurobiological basis for addiction, including natural or process addiction, and then discuss how this relates to our current understanding of sexuality as a natural reward that can become functionally "unmanageable" in an individual's life….

It is clear that the current definition and understanding of addiction has changed based with the infusion of knowledge regarding how the brain learns and desires. Whereas sexual addiction was formerly defined based solely on behavioral criteria, it is now seen also through the lens of neuromodulation. Those who will not or cannot understand these concepts may continue to cling to a more neurologically naïve perspective, but those who are able to comprehend the behavior in the context of the biology, this new paradigm provides an integrative and functional definition of sexual addiction which informs both the scientist and the clinician.

12) Neuroscientific Approaches to Online Pornography Addiction (Stark & Klucken, 2017) - Excerpts:

The availability of pornographic material has substantially increased with the development of the Internet. As a result of this, men ask for treatment more often because their pornography consumption intensity is out of control; i.e., they are not able to stop or reduce their problematic behavior although they are faced with negative consequences…. In the last two decades, several studies with neuroscientific approaches, especially functional magnetic resonance imaging (fMRI), were conducted to explore the neural correlates of watching pornography under experimental conditions and the neural correlates of excessive pornography use. Given previous results, excessive pornography consumption can be connected to already known neurobiological mechanisms underlying the development of substance-related addictions.

Finally, we summarized the studies, which investigated the correlates of excessive pornography consumption on a neural level. Despite a lack of longitudinal studies, it is plausible that the observed characteristics in men with sexual addiction are the results not the causes of excessive pornography consumption. Most of the studies report stronger cue reactivity in the reward circuit toward sexual material in excessive pornography users than in control subjects, which mirrors the findings of substance-related addictions. The results concerning a reduced prefrontal-striatal-connectivity in subjects with pornography addiction can be interpreted as a sign of an impaired cognitive control over the addictive behavior.

13) Is excessive sexual behaviour an addictive disorder? (Potenza et al., 2017) - Excerpts:

Compulsive sexual behaviour disorder (operationalised as hypersexual disorder) was considered for inclusion in DSM-5 but ultimately excluded, despite the generation of formal criteria and field trial testing. This exclusion has hindered prevention, research, and treatment efforts, and left clinicians without a formal diagnosis for compulsive sexual behaviour disorder.

Research into the neurobiology of compulsive sexual behaviour disorder has generated findings relating to attentional biases, incentive salience attributions, and brain-based cue reactivity that suggest substantial similarities with addictions. Compulsive sexual behaviour disorder is being proposed as an impulse-control disorder in ICD-11, consistent with a proposed view that craving, continued engagement despite adverse consequences, compulsive engagement, and diminished control represent core features of impulse-control disorders. This view might have been appropriate for some DSM-IV impulse-control disorders, specifically pathological gambling. However, these elements have long been considered central to addictions, and in the transition from DSM-IV to DSM-5, the category of Impulse Control Disorders Not Elsewhere Classified was restructured, with pathological gambling renamed and reclassified as an addictive disorder. At present, the ICD-11 beta draft site lists the impulse-control disorders, and includes compulsive sexual behaviour disorder, pyromania, kleptomania, and intermittent explosive disorder.

Compulsive sexual behaviour disorder seems to fit well with non-substance addictive disorders proposed for ICD-11, consistent with the narrower term of sex addiction currently proposed for compulsive sexual behaviour disorder on the ICD-11 draft website. We believe that classification of compulsive sexual behaviour disorder as an addictive disorder is consistent with recent data and might benefit clinicians, researchers, and individuals suffering from and personally affected by this disorder.

Neurological Studies (fMRI, MRI, EEG, Neuro-endocrine, Neuro-pyschological):

The neurological studies below are categorized in two ways. First by the addiction-related brain changes each reported. Below that the same studies are listed by date of publication, with excerpts and clarifications.

Lists by addiction-related brain change: The four major brain changes induced by addiction are described by George F. Koob and Nora D. Volkow in their landmark review. Koob is the Director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA), and Volkow is the director of the National Institute on Drug Abuse (NIDA). It was published in The New England Journal of Medicine: Neurobiologic Advances from the Brain Disease Model of Addiction (2016). The paper describes the major brain changes involved with both drug and behavioral addictions, while stating in its opening paragraph that sex addiction exists:

"We conclude that neuroscience continues to support the brain disease model of addiction. Neuroscience research in this area not only offers new opportunities for the prevention and treatment of substance addictions and related behavioral addictions (e.g., to food, sex, and gambling)...."

The Volkow & Koob paper outlined four fundamental addiction-caused brain changes, which are: 1) Sensitization, 2) Desensitization, 3) Dysfunctional prefrontal circuits (hypofrontality), 4) Malfunctioning stress system. All 4 of these brain changes have been identified among the many neurological studies listed on this page:  

  • Studies reporting sensitization (cue-reactivity & cravings) in porn users/sex addicts: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
  • Studies reporting desensitization or habituation (resulting in tolerance) in porn users/sex addicts: 1, 2, 3, 4, 5, 6.
  • Studies reporting poorer executive functioning (hypofrontality) or altered prefrontal activity in porn users/sex addicts: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13.
  • Studies indicating a dysfunctional stress system in porn users/sex addicts: 1, 2, 3.

Lists by date of publication: The following list contains all the neurological studies published on porn users and sex addicts. Each study listed below is accompanied by a description or excerpt, and indicates which of the 4 addiction-related brain change(s) just discussed its findings endorse:

1) Preliminary Investigation of The Impulsive And Neuroanatomical Characteristics of Compulsive Sexual Behavior (Miner et al., 2009) - [dysfunctional prefrontal circuits/poorer executive function] – fMRI study involving primarily sex addicts. Study reports more impulsive behavior in a Go-NoGo task in sex addicts (hypersexuals) compared to control participants. Brain scans revealed that sex addicts had disorganized prefrontal cortex white matter compared to controls. Excerpts:

In addition to the above self-report measures, CSB patients also showed significantly more impulsivity on a behavioral task, the Go-No Go procedure.

Results also indicate that CSB patients showed significantly higher superior frontal region mean diffusivity (MD) than controls. A correlational analysis indicated significant associations between impulsivity measures and inferior frontal region fractional anisotrophy (FA) and MD, but no associations with superior frontal region measures. Similar analyses indicated a significant negative association between superior frontal lobe MD and the compulsive sexual behavior inventory.

2) Self-reported differences on measures of executive function and hypersexual behavior in a patient and community sample of men (Reid et al., 2010) - [poorer executive function] – An excerpt:

Patients seeking help for hypersexual behavior often exhibit features of impulsivity, cognitive rigidity, poor judgment, deficits in emotion regulation, and excessive preoccupation with sex. Some of these characteristics are also common among patients presenting with neurological pathology associated with executive dysfunction. These observations led to the current investigation of differences between a group of hypersexual patients (n = 87) and a non-hypersexual community sample (n = 92) of men using the Behavior Rating Inventory of Executive Function-Adult Version  Hypersexual behavior was positively correlated with global indices of executive dysfunction and several subscales of the BRIEF-A. These findings provide preliminary evidence supporting the hypothesis that executive dysfunction may be implicated in hypersexual behavior.

3) Watching Pornographic Pictures on the Internet: Role of Sexual Arousal Ratings and Psychological-Psychiatric Symptoms for Using Internet Sex Sites Excessively (Brand et al., 2011) - [greater cravings/sensitization and poorer executive function] – An excerpt:

Results indicate that self-reported problems in daily life linked to online sexual activities were predicted by subjective sexual arousal ratings of the pornographic material, global severity of psychological symptoms, and the number of sex applications used when being on Internet sex sites in daily life, while the time spent on Internet sex sites (minutes per day) did not significantly contribute to explanation of variance in IATsex score. We see some parallels between cognitive and brain mechanisms potentially contributing to the maintenance of excessive cybersex and those described for individuals with substance dependence.

4) Pornographic Picture Processing Interferes with Working Memory Performance (Laier et al., 2013) - [greater cravings/sensitization and poorer executive function] – An excerpt:

Some individuals report problems during and after Internet sex engagement, such as missing sleep and forgetting appointments, which are associated with negative life consequences. One mechanism potentially leading to these kinds of problems is that sexual arousal during Internet sex might interfere with working memory (WM) capacity, resulting in a neglect of relevant environmental information and therefore disadvantageous decision making. Results revealed worse WM performance in the pornographic picture condition of the 4-back task compared with the three remaining picture conditions. Findings are discussed with respect to Internet addiction because WM interference by addiction-related cues is well known from substance dependencies.

5) Sexual Picture Processing Interferes with Decision-Making Under Ambiguity (Laier et al., 2013) - [greater cravings/sensitization and poorer executive function] – An excerpt:

Decision-making performance was worse when sexual pictures were associated with disadvantageous card decks compared to performance when the sexual pictures were linked to the advantageous decks. Subjective sexual arousal moderated the relationship between task condition and decision-making performance. This study emphasized that sexual arousal interfered with decision-making, which may explain why some individuals experience negative consequences in the context of cybersex use.

6) Cybersex addiction: Experienced sexual arousal when watching pornography and not real-life sexual contacts makes the difference (Laier et al., 2013) - [greater cravings/sensitization and poorer executive function] – An excerpt:

The results show that indicators of sexual arousal and craving to Internet pornographic cues predicted tendencies towards cybersex addiction in the first study. Moreover, it was shown that problematic cybersex users report greater sexual arousal and craving reactions resulting from pornographic cue presentation. In both studies, the number and the quality with real-life sexual contacts were not associated to cybersex addiction. The results support the gratification hypothesis, which assumes reinforcement, learning mechanisms, and craving to be relevant processes in the development and maintenance of cybersex addiction. Poor or unsatisfying sexual real life contacts cannot sufficiently explain cybersex addiction.

7) Sexual Desire, not Hypersexuality, is Related to Neurophysiological Responses Elicited by Sexual Images (Steele et al., 2013) - [greater cue-reactivity correlated with less sexual desire: sensitization and habituation] - This EEG study was touted in the media as evidence against the existence of porn/sex addiction. Not so. Steele et al. 2013 actually lends support to the existence of both porn addiction and porn use down-regulating sexual desire. How so? The study reported higher EEG readings (relative to neutral pictures) when subjects were briefly exposed to pornographic photos. Studies consistently show that an elevated P300 occurs when addicts are exposed to cues (such as images) related to their addiction.

In line with the Cambridge University brain scan studies, this EEG study also reported greater cue-reactivity to porn correlating with less desire for partnered sex. To put it another way - individuals with greater brain activation to porn would rather masturbate to porn than have sex with a real person. Shockingly, study spokesperson Nicole Prause claimed that porn users merely had "high libido," yet the results of the study say the exact opposite (subjects' desire for partnered sex was dropping in relation to their porn use). Five peer-reviewed papers explain the truth: 1, 2, 3, 4, 5. Also see an extensive YBOP critique.

Aside from the many unsupported claims in the press, it's disturbing that Prause's 2013 EGG study passed peer-review, as it suffered from serious methodological flaws: 1) subjects were heterogeneous (males, females, non-heterosexuals); 2) subjects were not screened for mental disorders or addictions; 3) study had no control group for comparison; 4) questionnaires were not validated for porn addiction.

8) Brain Structure and Functional Connectivity Associated With Pornography Consumption: The Brain on Porn (Kuhn & Gallinat, 2014) – [desensitization, habituation, and dysfunctional prefrontal circuits]. This Max Planck Institute fMRI study reported 3 neurological findings correlating with higher levels of porn use: (1) less reward system grey matter (dorsal striatum), (2) less reward circuit activation while briefly viewing sexual photos, (3) poorer functional connectivity between the dorsal striatum and dorsolateral prefrontal cortex. The researchers interpreted the 3 findings as an indication of the effects of longer-term porn exposure. Said the study,

This is in line with the hypothesis that intense exposure to pornographic stimuli results in a down-regulation of the natural neural response to sexual stimuli.

In describing the poorer functional connectivity between the PFC and the striatum the study said,

Dysfunction of this circuitry has been related to inappropriate behavioral choices, such as drug seeking, regardless of the potential negative outcome

Lead author Simone Kühn commenting in an article about the findings said:

We assume that subjects with a high porn consumption need increasing stimulation to receive the same amount of reward. That could mean that regular consumption of pornography more or less wears out your reward system. That would fit perfectly the hypothesis that their reward systems need growing stimulation.

9) Neural Correlates of Sexual Cue Reactivity in Individuals with and without Compulsive Sexual Behaviours (Voon et al., 2014) – [sensitization/cue-reactivity and desensitization] The first in a series of Cambridge University studies found the same brain activity pattern in porn addicts (CSB subjects) as seen in drug addicts and alcoholics – greater cue-reactivity or sensitization. Lead researcher Valerie Voon said:

There are clear differences in brain activity between patients who have compulsive sexual behaviour and healthy volunteers. These differences mirror those of drug addicts.

Voon et al., 2014 also found that porn addicts fit the accepted addiction model of wanting "it" more, but not liking "it" any more. Excerpt:

Compared to healthy volunteers, CSB subjects had greater subjective sexual desire or wanting to explicit cues and had greater liking scores to erotic cues, thus demonstrating a dissociation between wanting and liking

The researchers also reported that 60% of subjects (average age: 25) had difficulty achieving erections/arousal with real partners, yet could achieve erections with porn. This indicates sensitization or habituation. Excerpts:

CSB subjects reported that as a result of excessive use of sexually explicit materials..... experienced diminished libido or erectile function specifically in physical relationships with women (although not in relationship to the sexually explicit material)…

CSB subjects compared to healthy volunteers had significantly more difficulty with sexual arousal and experienced more erectile difficulties in intimate sexual relationships but not to sexually explicit material.

10) Enhanced Attentional Bias towards Sexually Explicit Cues in Individuals with and without Compulsive Sexual Behaviours (Mechelmans et al., 2014) - [sensitization/cue-reactivity] - The second Cambridge University study. An excerpt:

Our findings of enhanced attentional bias... suggest possible overlaps with enhanced attentional bias observed in studies of drug cues in disorders of addictions. These findings converge with recent findings of neural reactivity to sexually explicit cues in [porn addicts] in a network similar to that implicated in drug-cue-reactivity studies and provide support for incentive motivation theories of addiction underlying the aberrant response to sexual cues in [porn addicts]. This finding dovetails with our recent observation that sexually explicit videos were associated with greater activity in a neural network similar to that observed in drug-cue-reactivity studies. Greater desire or wanting rather than liking was further associated with activity in this neural network. These studies together provide support for an incentive motivation theory of addiction underlying the aberrant response towards sexual cues in CSB.

11) Cybersex addiction in heterosexual female users of internet pornography can be explained by gratification hypothesis (Laier et al., 2014) - [greater cravings/sensitization] - An excerpt:

We examined 51 female IPU and 51 female non-Internet pornography users (NIPU). Using questionnaires, we assessed the severity of cybersex addiction in general, as well as propensity for sexual excitation, general problematic sexual behavior, and severity of psychological symptoms. Additionally, an experimental paradigm, including a subjective arousal rating of 100 pornographic pictures, as well as indicators of craving, was conducted. Results indicated that IPU rated pornographic pictures as more arousing and reported greater craving due to pornographic picture presentation compared with NIPU. Moreover, craving, sexual arousal rating of pictures, sensitivity to sexual excitation, problematic sexual behavior, and severity of psychological symptoms predicted tendencies toward cybersex addiction in IPU. Being in a relationship, number of sexual contacts, satisfaction with sexual contacts, and use of interactive cybersex were not associated with cybersex addiction. These results are in line with those reported for heterosexual males in previous studies. Findings regarding the reinforcing nature of sexual arousal, the mechanisms of learning, and the role of cue reactivity and craving in the development of cybersex addiction in IPU need to be discussed.

12) Empirical Evidence and Theoretical Considerations on Factors Contributing to Cybersex Addiction From a Cognitive Behavioral View (Laier et al., 2014) - [greater cravings/sensitization] - An excerpt:

The nature of a phenomenon often called cybersex addiction (CA) and its mechanisms of development are discussed. Previous work suggests that some individuals might be vulnerable to CA, while positive reinforcement and cue-reactivity are considered to be core mechanisms of CA development. In this study, 155 heterosexual males rated 100 pornographic pictures and indicated their increase of sexual arousal. Moreover, tendencies towards CA, sensitivity to sexual excitation, and dysfunctional use of sex in general were assessed. The results of the study show that there are factors of vulnerability to CA and provide evidence for the role of sexual gratification and dysfunctional coping in the development of CA.

13) Novelty, Conditioning and Attentional Bias to Sexual Rewards (Banca et al., 2015) - [greater cravings/sensitization and habituation/desensitization] - Another Cambridge University fMRI study. Compared to controls porn addicts preferred sexual novelty and conditioned cues associated porn. However, the brains of porn addicts habituated faster to sexual images. Since novelty preference wasn't pre-existing, it is believed that porn addiction drives novelty-seeking in an attempt to overcome habituation and desensitization.

Compulsive sexual behavior (CSB) was associated with enhanced novelty preference for sexual, as compared to control images, and a generalized preference for cues conditioned to sexual and monetary versus neutral outcomes compared to healthy volunteers. CSB individuals also had greater dorsal cingulate habituation to repeated sexual versus monetary images with the degree of habituation correlating with enhanced preference for sexual novelty. Approach behaviors to sexually conditioned cues dissociable from novelty preference were associated with an early attentional bias to sexual images. This study shows that CSB individuals have a dysfunctional enhanced preference for sexual novelty possibly mediated by greater cingulate habituation along with a generalized enhancement of conditioning to rewards. An excerpt:

An excerpt from the related press release:

They found that when the sex addicts viewed the same sexual image repeatedly, compared to the healthy volunteers they experienced a greater decrease of activity in the region of the brain known as the dorsal anterior cingulate cortex, known to be involved in anticipating rewards and responding to new events. This is consistent with 'habituation', where the addict finds the same stimulus less and less rewarding – for example, a coffee drinker may get a caffeine 'buzz' from their first cup, but over time the more they drink coffee, the smaller the buzz becomes.

This same habituation effect occurs in healthy males who are repeatedly shown the same porn video. But when they then view a new video, the level of interest and arousal goes back to the original level. This implies that, to prevent habituation, the sex addict would need to seek out a constant supply of new images. In other words, habituation could drive the search for novel images.

"Our findings are particularly relevant in the context of online pornography," adds Dr Voon. "It's not clear what triggers sex addiction in the first place and it is likely that some people are more pre-disposed to the addiction than others, but the seemingly endless supply of novel sexual images available online helps feed their addiction, making it more and more difficult to escape."

14) Neural Substrates of Sexual Desire in Individuals with Problematic Hypersexual Behavior (Seok & Sohn, 2015) - [greater cue reactivity/sensitization and dysfunctional prefrontal circuits] - This Korean fMRI study replicates other brain studies on porn users. Like the Cambridge University studies it found cue-induced brain activation patterns in sex addicts, which mirrored the patterns of drug addicts. In line with several German studies it found alterations in the prefrontal cortex which match the changes observed in drug addicts. What's new is that the findings matched the prefrontal cortex activation patterns observed in drug addicts: Greater cue-reactivity to sexual images yet inhibited responses to other normally salient stimuli. An excerpt:

Our study aimed to investigate the neural correlates of sexual desire with event-related functional magnetic resonance imaging (fMRI). Twenty-three individuals with PHB and 22 age-matched healthy controls were scanned while they passively viewed sexual and nonsexual stimuli. The subjects' levels of sexual desire were assessed in response to each sexual stimulus. Relative to controls, individuals with PHB experienced more frequent and enhanced sexual desire during exposure to sexual stimuli. Greater activation was observed in the caudate nucleus, inferior parietal lobe, dorsal anterior cingulate gyrus, thalamus, and dorsolateral prefrontal cortex in the PHB group than in the control group. In addition, the hemodynamic patterns in the activated areas differed between the groups. Consistent with the findings of brain imaging studies of substance and behavior addiction, individuals with the behavioral characteristics of PHB and enhanced desire exhibited altered activation in the prefrontal cortex and subcortical regions

15) Modulation of Late Positive Potentials by Sexual Images in Problem Users and Controls Inconsistent with "Porn Addiction" (Prause et al., 2015) – [habituation] - A second EEG study from Prause's team. This study compared the 2013 subjects from Steele et al., 2013 to an actual control group (yet it suffered from the same methodological flaws named above). The results: Compared to controls "individuals experiencing problems regulating their porn viewing" had lower brain responses to one-second exposure to photos of vanilla porn. The lead author claims these results "debunk porn addiction." What legitimate scientist would claim that their lone anomalous study has debunked a well established field of study?

In reality, the findings of Prause et al. 2015 align perfectly with Kühn & Gallinat (2014), which found that more porn use correlated with less brain activation in response to pictures of vanilla porn. Prause et al findings also align with Banca et al. 2015 which is #13 in this list. Moreover, another EEG study found that greater porn use in women correlated with less brain activation to porn. Lower EEG readings mean that subjects are paying less attention to the pictures. Put simply, frequent porn users were desensitized to static images of vanilla porn. They were bored (habituated or desensitized). See this extensive YBOP critique. Six peer-reviewed papers agree that this study actually found desensitization/habituation in frequent porn users (consistent with addiction): 1, 2, 3, 4, 5, 6.

16) HPA Axis Dysregulation in Men With Hypersexual Disorder (Chatzittofis, 2015) - [dysfunctional stress response] - A study with 67 male sex addicts and 39 age-matched controls. The Hypothalamus-Pituitary-Adrenal (HPA) axis is the central player in our stress response. Addictions alter the brain's stress circuits leading to a dysfunctional HPA axis. This study on sex addicts (hypersexuals) found altered stress responses that mirror the findings with substance addictions. Excerpts from press release:

The study involved 67 men with hypersexual disorder and 39 healthy matched controls. The participants were carefully diagnosed for hypersexual disorder and any co-morbidity with depression or childhood trauma. The researchers gave them a low dose of dexamethasone on the evening before the test to inhibit their physiological stress response, and then in the morning measured their levels of stress hormones cortisol and ACTH. They found that patients with hypersexual disorder had higher levels of such hormones than the healthy controls, a difference that remained even after controlling for co-morbid depression and childhood trauma.

"Aberrant stress regulation has previously been observed in depressed and suicidal patients as well as in substance abusers," says Professor Jokinen. "In recent years, the focus has been on whether childhood trauma can lead to a dysregulation of the body's stress systems via so-called epigenetic mechanisms, in other words how their psychosocial environments can influence the genes that control these systems." According to the researchers, the results suggest that the same neurobiological system involved in another type of abuse can apply to people with hypersexual disorder.

17) Prefrontal control and internet addiction: a theoretical model and review of neuropsychological and neuroimaging findings (Brand et al., 2015) - [dysfunctional prefrontal circuits/poorer executive function and sensitization] – Excerpt:

Consistent with this, results from functional neuroimaging and other neuropsychological studies demonstrate that cue-reactivity, craving, and decision making are important concepts for understanding Internet addiction. The findings on reductions in executive control are consistent with other behavioral addictions, such as pathological gambling. They also emphasize the classification of the phenomenon as an addiction, because there are also several similarities with findings in substance dependency.  Moreover, the results of the current study are comparable to findings from substance dependency research and emphasize analogies between cybersex addiction and substance dependencies or other behavioral addictions.

18) Implicit associations in cybersex addiction: Adaption of an Implicit Association Test with pornographic pictures (Snagkowski et al., 2015) - [greater cravings/sensitization] – Excerpt:

Recent studies show similarities between cybersex addiction and substance dependencies and argue to classify cybersex addiction as a behavioral addiction. In substance dependency, implicit associations are known to play a crucial role, and such implicit associations have not been studied in cybersex addiction, so far. In this experimental study, 128 heterosexual male participants completed an Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) modified with pornographic pictures. Further, problematic sexual behavior, sensitivity towards sexual excitation, tendencies towards cybersex addiction, and subjective craving due to watching pornographic pictures were assessed. Results show positive relationships between implicit associations of pornographic pictures with positive emotions and tendencies towards cybersex addiction, problematic sexual behavior, sensitivity towards sexual excitation as well as subjective craving. Moreover, a moderated regression analysis revealed that individuals who reported high subjective craving and showed positive implicit associations of pornographic pictures with positive emotions, particularly tended towards cybersex addiction. The findings suggest a potential role of positive implicit associations with pornographic pictures in the development and maintenance of cybersex addiction. Moreover, the results of the current study are comparable to findings from substance dependency research and emphasize analogies between cybersex addiction and substance dependencies or other behavioral addictions.

19) Symptoms of cybersex addiction can be linked to both approaching and avoiding pornographic stimuli: results from an analog sample of regular cybersex users (Snagkowski, et al., 2015) - [greater cravings/sensitization] – Excerpt:

Some approaches point toward similarities to substance dependencies for which approach/avoidance tendencies are crucial mechanisms. Several researchers have argued that within an addiction-related decision situation, individuals might either show tendencies to approach or avoid addiction-related stimuli. In the current study 123 heterosexual males completed an Approach-Avoidance-Task (AAT; Rinck and Becker, 2007) modified with pornographic pictures. During the AAT participants either had to push pornographic stimuli away or pull them toward themselves with a joystick. Sensitivity toward sexual excitation, problematic sexual behavior, and tendencies toward cybersex addiction were assessed with questionnaires.

Results showed that individuals with tendencies toward cybersex addiction tended to either approach or avoid pornographic stimuli. Additionally, moderated regression analyses revealed that individuals with high sexual excitation and problematic sexual behavior who showed high approach/avoidance tendencies, reported higher symptoms of cybersex addiction. Analogous to substance dependencies, results suggest that both approach and avoidance tendencies might play a role in cybersex addiction. Moreover, an interaction with sensitivity toward sexual excitation and problematic sexual behavior could have an accumulating effect on the severity of subjective complaints in everyday life due to cybersex use. The findings provide further empirical evidence for similarities between cybersex addiction and substance dependencies. Such similarities could be retraced to a comparable neural processing of cybersex- and drug-related cues.

20) Getting stuck with pornography? Overuse or neglect of cybersex cues in a multitasking situation is related to symptoms of cybersex addiction (Schiebener et al., 2015) - [greater cravings/sensitization and poorer executive control] – Excerpt:

Some individuals consume cybersex contents, such as pornographic material, in an addictive manner, which leads to severe negative consequences in private life or work. One mechanism leading to negative consequences may be reduced executive control over cognition and behavior that may be necessary to realize goal-oriented switching between cybersex use and other tasks and obligations of life. To address this aspect, we investigated 104 male participants with an executive multitasking paradigm with two sets: One set consisted of pictures of persons, the other set consisted of pornographic pictures. In both sets the pictures had to be classified according to certain criteria. The explicit goal was to work on all classification tasks to equal amounts, by switching between the sets and classification tasks in a balanced manner.

We found that less balanced performance in this multitasking paradigm was associated with a higher tendency towards cybersex addiction. Persons with this tendency often either overused or neglected working on the pornographic pictures. The results indicate that reduced executive control over multitasking performance, when being confronted with pornographic material, may contribute to dysfunctional behaviors and negative consequences resulting from cybersex addiction. However, individuals with tendencies towards cybersex addiction seem to have either an inclination to avoid or to approach the pornographic material, as discussed in motivational models of addiction.

21) Trading Later Rewards for Current Pleasure: Pornography Consumption and Delay Discounting (Negash et al., 2015) - [poorer executive control: causation experiment] – Excerpts:

Study 1: Participants completed a pornography use questionnaire and a delay discounting task at Time 1 and then again four weeks later. Participants reporting higher initial pornography use demonstrated a higher delay discounting rate at Time 2, controlling for initial delay discounting. Study 2:  Participants who abstained from pornography use demonstrated lower delay discounting than participants who abstained from their favorite food.

Internet pornography is a sexual reward that contributes to delay discounting differently than other natural rewards do, even when use is not compulsive or addictive. This research makes an important contribution, demonstrating that the effect goes beyond temporary arousal.

Pornography consumption may provide immediate sexual gratification but can have implications that transcend and affect other domains of a person’s life, especially relationships.

The finding suggests that Internet pornography is a sexual reward that contributes to delay discounting differently than other natural rewards. It is therefore important to treat pornography as a unique stimulus in reward, impulsivity, and addiction studies and to apply this accordingly in individual as well as relational treatment.

22) Sexual Excitability and Dysfunctional Coping Determine Cybersex Addiction in Homosexual Males (Laier et al., 2015) - [greater cravings/sensitization] – Excerpt:

Recent findings have demonstrated an association between CyberSex Addiction (CA) severity and indicators of sexual excitability, and that coping by sexual behaviors mediated the relationship between sexual excitability and CA symptoms. The aim of this study was to test this mediation in a sample of homosexual males. Questionnaires assessed symptoms of CA, sensitivity to sexual excitation, pornography use motivation, problematic sexual behavior, psychological symptoms, and sexual behaviors in real life and online. Moreover, participants viewed pornographic videos and indicated their sexual arousal before and after the video presentation. Results showed strong correlations between CA symptoms and indicators of sexual arousal and sexual excitability, coping by sexual behaviors, and psychological symptoms. CA was not associated with offline sexual behaviors and weekly cybersex use time. Coping by sexual behaviors partially mediated the relationship between sexual excitability and CA. The results are comparable with those reported for heterosexual males and females in previous studies and are discussed against the background of theoretical assumptions of CA, which highlight the role of positive and negative reinforcement due to cybersex use.

23) The Role of Neuroinflammation in the Pathophysiology of Hypersexual Disorder (Jokinen et al., 2016) - [dysfunctional stress response and neuro-inflammation] - This study reported higher levels of circulating Tumor Necrosis Factor (TNF) in sex addicts when compared to healthy controls. Elevated levels of TNF (a marker of inflammation) have also been found in substance abusers and drug-addicted animals (alcohol, heroin, meth). There were strong correlations between TNF levels and rating scales measuring hypersexuality.

24) Compulsive Sexual Behavior: Prefrontal And Limbic Volume and Interactions (Schmidt et al., 2016) - [dysfunctional prefrontal circuits and sensitization] - This is an fMRI study. Compared to healthy controls CSB subjects (porn addicts) had increased left amygdala volume and reduced functional connectivity between the amygdala and dorsolateral prefrontal cortex DLPFC. Reduced functional connectivity between the amygdala and the prefrontal cortex aligns with substance addictions. It is thought that poorer connectivity diminishes the prefrontal cortex's control over a user's impulse to engage in the addictive behavior. This study suggests that drug toxicity may lead to less grey matter and thus reduced amygdala volume in drug addicts. The amygdala is consistently active during porn viewing, especially during initial exposure to a sexual cue. Perhaps the constant sexual novelty and searching and seeking leads to a unique effect on the amygdala in compulsive porn users. Alternatively, years of porn addiction and severe negative consequences are very stressful - and chronic social stress is related to increased amygdala volume. Study #16 above found that "sex addicts" have an overactive stress system. Could the chronic stress related to porn/sex addiction, along with factors that make sex unique, lead to greater amygdala volume? An excerpt:

Our current findings highlight elevated volumes in a region implicated in motivational salience and lower resting state connectivity of prefrontal top-down regulatory control networks. Disruption of such networks may explain the aberrant behavioral patterns toward environmentally salient reward or enhanced reactivity to salient incentive cues. Although our volumetric findings contrast with those in SUD, these findings may reflect differences as a function of the neurotoxic effects of chronic drug exposure. Emerging evidence suggests potential overlaps with an addiction process particularly supporting incentive motivation theories. We have shown that activity in this salience network is then enhanced following exposure to highly salient or preferred sexually explicit cues [Brand et al., 2016; Seok and Sohn, 2015; Voon et al., 2014] along with enhanced attentional bias [Mechelmans et al., 2014] and desire specific to the sexual cue but not generalized sexual desire [Brand et al., 2016; Voon et al., 2014]. Enhanced attention to sexually explicit cues is further associated with preference for sexually conditioned cues thus confirming the relationship between sexual cue conditioning and attentional bias [Banca et al., 2016]. These findings of enhanced activity related to sexually conditioned cues differ from that of the outcome (or the unconditioned stimulus) in which enhanced habituation, possibly consistent with the concept of tolerance, increases the preference for novel sexual stimuli [Banca et al., 2016]. Together these findings help elucidate the underlying neurobiology of CSB leading toward a greater understanding of the disorder and identification of possible therapeutic markers.

25) Ventral Striatum Activity When Watching Preferred Pornographic Pictures is Correlated With Symptoms of Internet Pornography Addiction (Brand et al., 2016) - [greater cue reactivity/sensitization] – A German fMRI study. Finding #1: Reward center activity (ventral striatum) was higher for preferred pornographic pictures. Finding #2: Ventral striatum reactivity correlated with the internet sex addiction score. Both findings indicate sensitization and align with the addiction model. The authors state that the "Neural basis of Internet pornography addiction is comparable to other addictions." An excerpt:

One type of Internet addiction is excessive pornography consumption, also referred to as cybersex or Internet pornography addiction. Neuroimaging studies found ventral striatum activity when participants watched explicit sexual stimuli compared to non-explicit sexual/erotic material. We now hypothesized that the ventral striatum should respond to preferred pornographic compared to non-preferred pornographic pictures and that the ventral striatum activity in this contrast should be correlated with subjective symptoms of Internet pornography addiction. We studied 19 heterosexual male participants with a picture paradigm including preferred and non-preferred pornographic material.

Pictures from the preferred category were rated as more arousing, less unpleasant, and closer to ideal. Ventral striatum response was stronger for the preferred condition compared to non-preferred pictures. Ventral striatum activity in this contrast was correlated with the self-reported symptoms of Internet pornography addiction. The subjective symptom severity was also the only significant predictor in a regression analysis with ventral striatum response as dependent variable and subjective symptoms of Internet pornography addiction, general sexual excitability, hypersexual behavior, depression, interpersonal sensitivity, and sexual behavior in the last days as predictors. The results support the role for the ventral striatum in processing reward anticipation and gratification linked to subjectively preferred pornographic material. Mechanisms for reward anticipation in ventral striatum may contribute to a neural explanation of why individuals with certain preferences and sexual fantasies are at-risk for losing their control over Internet pornography consumption.

26) Altered Appetitive Conditioning and Neural Connectivity in Subjects With Compulsive Sexual Behavior (Klucken et al., 2016) - [greater cue reactivity/sensitization and dysfunctional prefrontal circuits] - This German fMRI study replicated two major findings from Voon et al., 2014 and Kuhn & Gallinat 2014. Main Findings: The neural correlates of appetitive conditioning and neural connectivity were altered in the CSB group. According to the researchers, the first alteration - heightened amygdala activation - might reflect facilitated conditioning (greater "wiring" to previously neutral cues predicting porn images). The second alteration - decreased connectivity between the ventral striatum and the prefrontal cortex - could be a marker for impaired ability to control impulses. Said the researchers, "These [alterations] are in line with other studies investigating the neural correlates of addiction disorders and impulse control deficits." The findings of greater amygdalar activation to cues (sensitization) and decreased connectivity between the reward center and the prefrontal cortex (hypofrontality) are two of the major brain changes seen in substance addiction. In addition, 3 of the 20 compulsive porn users suffered from "orgasmic-erection disorder." An excerpt:

In general, the observed increased amygdala activity and the concurrently decreased ventral striatal-PFC coupling allows speculations about the etiology and treatment of CSB. Subjects with CSB seemed more prone to establish associations between formally neutral cues and sexually relevant environmental stimuli. Thus, these subjects are more likely to encounter cues that elicit approaching behavior. Whether this leads to CSB or is a result of CSB must be answered by future research. In addition, impaired regulation processes, which are reflected in the decreased ventral striatal-prefrontal coupling, might further support the maintenance of the problematic behavior.

27) Compulsivity Across the Pathological Misuse of Drug and Non-Drug Rewards (Banca et al., 2016) - [greater cue reactivity/sensitization, enhanced conditioned responses] - This Cambridge University fMRI study compares aspects of compulsivity in alcoholics, binge-eaters, video game addicts and porn addicts (CSB). Excerpts:

In contrast to other disorders, CSB compared to HV showed faster acquisition to reward outcomes along with a greater perseveration in the reward condition irrespective of outcome. The CSB subjects did not show any specific impairments in set shifting or reversal learning. These findings converge with our previous findings of enhanced preference for stimuli conditioned to either sexual or monetary outcomes, overall suggesting enhanced sensitivity to rewards (Banca et al., 2016). Further studies using salient rewards are indicated.

28) Subjective Craving for Pornography and Associative Learning Predict Tendencies Towards Cybersex Addiction in a Sample of Regular Cybersex Users (Snagkowski et al., 2016) - [greater cue reactivity/sensitization, enhanced conditioned responses] – This unique study conditioned subjects to formerly neutral shapes, which predicted the appearance of a pornographic image. Excerpts:

There is no consensus regarding the diagnostic criteria of cybersex addiction. Some approaches postulate similarities to substance dependencies, for which associative learning is a crucial mechanism. In this study, 86 heterosexual males completed a Standard Pavlovian to Instrumental Transfer Task modified with pornographic pictures to investigate associative learning in cybersex addiction. Additionally, subjective craving due to watching pornographic pictures and tendencies towards cybersex addiction were assessed. Results showed an effect of subjective craving on tendencies towards cybersex addiction, moderated by associative learning. Overall, these findings point towards a crucial role of associative learning for the development of cybersex addiction, while providing further empirical evidence for similarities between substance dependencies and cybersex addiction. In summary, the results of the current study suggest that associative learning might play a crucial role regarding the development of cybersex addiction. Our findings provide further evidence for similarities between cybersex addiction and substance dependencies since influences of subjective craving and associative learning were shown.

29) Mood changes after watching pornography on the Internet are linked to symptoms of Internet-pornography-viewing disorder (Laier & Brand, 2016) - [greater cravings/sensitization, less liking] - Excerpts:

The main results of the study are that tendencies towards Internet Pornography Disorder (IPD) were associated negatively with feeling generally good, awake, and calm as well as positively with perceived stress in daily life and the motivation to use Internet pornography in terms of excitation seeking and emotional avoidance.  Furthermore, tendencies towards IPD were negatively related to mood before and after watching Internet pornography as well as an actual increase of good and calm mood. The relationship between tendencies towards IPD and excitement seeking due to Internet-pornography use was moderated by the evaluation of the experienced orgasm's satisfaction. Generally, the results of the study are in line with the hypothesis that IPD is linked to the motivation to find sexual gratification and to avoid or to cope with aversive emotions as well as with the assumption that mood changes following pornography consumption are linked to IPD (Cooper et al., 1999 and Laier and Brand, 2014).

30) Problematic sexual behavior in young adults: Associations across clinical, behavioral, and neurocognitive variables (2016) - [poorer executive functioning] - Individuals with Problematic Sexual Behaviors (PSB) exhibited several neuro-cognitive deficits. These findings indicate poorer executive functioning (hypofrontality) which is a key brain feature occurring in drug addicts. A few excerpts:

One notable result from this analysis is that PSB shows significant associations with a number of deleterious clinical factors, including lower self-esteem, decreased quality of life, elevated BMI, and higher comorbidity rates for several disorders…

…it is also possible that the clinical features identified in the PSB group are actually the result of a tertiary variable which gives rise to both PSB and the other clinical features. One potential factor filling this role could be the neurocognitive deficits identified in the PSB group, particularly those relating to working memory, impulsivity/impulse control, and decision making. From this characterization, it is be possible to trace the problems evident in PSB and additional clinical features, such as emotional dysregulation, to particular cognitive deficits…

If the cognitive problems identified in this analysis are actually the core feature of PSB, this may have notable clinical implications.

31) Methylation of HPA Axis Related Genes in Men With Hypersexual Disorder (Jokinen et al., 2017) - [dysfunctional stress response, epigenetic changes] - This is a follow-up of #16 above which found that sex addicts have dysfunctional stress systems - a key neuro-endocrine change caused by addiction. The current study found epigenetic changes on genes central to the human stress response and closely associated with addiction. With epigenetic changes, the DNA sequence isn't altered (as happens with a mutation). Instead, the gene is tagged and its expression is turned up or down (short video explaining epigenetics). The epigenetic changes reported in this study resulted in altered CRF gene activity. CRF is a neurotransmitter and hormone that drives addictive behaviors such as cravings, and is a major player in many of the withdrawal symptoms experienced in connection with substance and behavioral addictions, including porn addiction.

32) Exploring the Relationship between Sexual Compulsivity and Attentional Bias to Sex-Related Words in a Cohort of Sexually Active Individuals (Albery et al., 2017) - [greater cue reactivity/sensitization, desensitization] - This study replicates the findings of this 2014 Cambridge University study, which compared the attentional bias of porn addicts to healthy controls. Here's what's new: The study correlated the "years of sexual activity" with 1) the sex addiction scores and also 2) the results of the attentional bias task. Among those scoring high on sexual addiction, fewer years of sexual experience were related to greater attentional bias (explanation of attentional bias). So higher sexual compulsivity scores + fewer years of sexual experience = greater signs of addiction (greater attentional bias, or interference). But attentional bias declines sharply in the compulsive users, and disappears at the highest number of years of sexual experience. The authors concluded that this result could indicate that more years of "compulsive sexual activity" lead to greater habituation or a general numbing of the pleasure response (desensitization). An excerpt from the conclusion:

One possible explanation for these results is that as a sexually compulsive individual engages in more compulsive behaviour, an associated arousal template develops [36–38] and that over time, more extreme behaviour is required for the same level of arousal to be realised. It is further argued that as an individual engages in more compulsive behaviour, neuropathways become desensitized to more ‘normalised’ sexual stimuli or images and individuals turn to more ‘extreme’ stimuli to realise the arousal desired. This is in accordance with work showing that ‘healthy’ males become habituated to explicit stimuli over time and that this habituation is characterised by decreased arousal and appetitive responses [39]. This suggests that more compulsive, sexually active participants have become ‘numb’ or more indifferent to the ‘normalised’ sex-related words used in the present study and as such display decreased attentional bias, while those with increased compulsivity and less experience still showed interference because the stimuli reflect more sensitised cognition.

33) Executive Functioning of Sexually Compulsive and Non-Sexually Compulsive Men Before and After Watching an Erotic Video (Messina et al., 2017) - [poorer executive functioning, greater cravings/sensitization] - Exposure to porn affected executive functioning in men with "compulsive sexual behaviors," but not healthy controls. Poorer executive functioning when exposed to addiction-related cues is a hallmark of substance disorders (indicating both altered prefrontal circuits and sensitization). Excerpts:

This finding indicates better cognitive flexibility after sexual stimulation by controls compared with sexually compulsive participants. These data support the idea that sexually compulsive men do not to take advantage of the possible learning effect from experience, which could result in better behavior modification. This also could be understood as a lack of a learning effect by the sexually compulsive group when they were sexually stimulated, similar to what happens in the cycle of sexual addiction, which starts with an increasing amount of sexual cognition, followed by the activation of sexual scripts and then orgasm, very often involving exposure to risky situations.

34) Can Pornography be Addictive? An fMRI Study of Men Seeking Treatment for Problematic Pornography Use (Gola et al., 2017) - [greater cue reactivity/sensitization, enhanced conditioned responses] – An fMRI study involving a unique cue-reactivity paradigm where formerly neutral shapes predicted the appearance of pornographic images. Excerpts:

Men with and without problematic porn use (PPU) differed in brain reactions to cues predicting erotic pictures, but not in reactions to erotic pictures themselves, consistent with the incentive salience theory of addictions. This brain activation was accompanied by increased behavioral motivation to view erotic images (higher 'wanting'). Ventral striatal reactivity for cues predicting erotic pictures was significantly related to the severity of PPU, amount of pornography use per week and number of weekly masturbations. Our findings suggest that like in substance-use and gambling disorders the neural and behavioral mechanisms linked to anticipatory processing of cues relate importantly to clinically relevant features of PPU. These findings suggest that PPU may represent a behavioral addiction and that interventions helpful in targeting behavioral and substance addictions warrant consideration for adaptation and use in helping men with PPU.

35) Conscious and Non-Conscious Measures of Emotion: Do They Vary with Frequency of Pornography Use? (Kunaharan et al., 2017) - [habituation or desensitization] - Study assessed porn users' responses (EEG readings & Startle Response) to various emotion-inducing images - including erotica. The study found several neurological differences between low frequency porn users and high frequency porn users. Excerpts:

Findings suggest that increased pornography use appears to have an influence on the brain’s non-conscious responses to emotion-inducing stimuli which was not shown by explicit self-report.

4.1. Explicit Ratings: Interestingly, the high porn use group rated the erotic images as more unpleasant than the medium use group. The authors suggest this may be due to the relatively “soft-core” nature of the “erotic” images contained in the IAPS database not providing the level of stimulation that they may usually seek out, as it has been shown by Harper and Hodgins [58] that with frequent viewing of pornographic material, many individuals often escalate into viewing more intense material to maintain the same level of physiological arousal. The “pleasant” emotion category saw valence ratings by all three groups to be relatively similar with the high use group rating the images as slightly more unpleasant on average than the other groups. This may again be due to the “pleasant” images presented not being stimulating enough for the individuals in the high use group. Studies have consistently shown a physiological downregulation in processing of appetitive content due to habituation effects in individuals who frequently seek out pornographic material [3, 7, 8]. It is the authors’ contention that this effect may account for the results observed.

4.3. Startle Reflex Modulation (SRM): The relative higher amplitude startle effect seen in the low and medium porn use groups may be explained by those in the group intentionally avoiding the use of pornography, as they may find it to be relatively more unpleasant. Alternatively, the results obtained also may be due to a habituation effect, whereby individuals in these groups do watch more pornography than they explicitly stated—possibly due to reasons of embarrassment among others, as habituation effects have been shown to increase startle eye blink responses [41, 42].

36) Exposure to Sexual Stimuli Induces Greater Discounting Leading to Increased Involvement in Cyber Delinquency Among Men (Cheng & Chiou, 2017) - [poorer executive functioning, greater impulsivity - causation experiment] - In two studies exposure to visual sexual stimuli resulted in: 1) greater delayed discounting (inability to delay gratification), 2) greater inclination to engage in cyber-delinquency, 3) greater inclination to purchase counterfeit goods and hack someone's Facebook account. Taken together this indicates that porn use increases impulsivity and may reduce certain executive functions (self-control, judgment, foreseeing consequences, impulse control). Excerpt:

People frequently encounter sexual stimuli during Internet use. Research has shown that stimuli inducing sexual motivation can lead to greater impulsivity in men, as manifested in greater temporal discounting (i.e., a tendency to prefer smaller, immediate gains to larger, future ones).

In conclusion, the current results demonstrate an association between sexual stimuli (e.g., exposure to pictures of sexy women or sexually arousing clothing) and men’s involvement in cyber delinquency. Our findings suggest that men’s impulsivity and self-control, as manifested by temporal discounting, are susceptible to failure in the face of ubiquitous sexual stimuli. Men may benefit from monitoring whether exposure to sexual stimuli is associated with their subsequent delinquent choices and behavior. Our findings suggest that encountering sexual stimuli can tempt men down the road of cyber delinquency

The current results suggest that the high availability of sexual stimuli in cyberspace may be more closely associated with men's cyber-delinquent behavior than previously thought.

37) Predictors for (Problematic) Use of Internet Sexually Explicit Material: Role of Trait Sexual Motivation and Implicit Approach Tendencies Towards Sexually Explicit Material (Stark et al., 2017) - [greater cue reactivity/sensitization/cravings] - Excerpts: 

The present study investigated whether trait sexual motivation and implicit approach tendencies toward sexual material are predictors of problematic SEM use and of the daily time spent watching SEM. In a behavioral experiment, we used the Approach-Avoidance Task (AAT) for measuring implicit approach tendencies towards sexual material. A positive correlation between implicit approach tendency towards SEM and the daily time spent on watching SEM might be explained by attentional effects: A high implicit approach tendency can be interpreted as an attentional bias towards SEM. A subject with this attentional bias might be more attracted to sexual cues on the Internet resulting in higher amounts of time spent on SEM sites.

Together these neurological studies found:

  1. The 3 major addiction-related brain changes: sensitization, desensitization, and hypofrontality.
  2. More porn use correlated with less grey matter in the reward circuit (dorsal striatum).
  3. More porn use correlated with less reward circuit activation when briefly viewing sexual images.
  4. More porn use correlated with disrupted neural connections between the reward circuit and prefrontal cortex.
  5. Addicts had greater prefrontal activity to sexual cues, but less brain activity to normal stimuli (matches drug addiction).
  6. 60% of compulsive porn addicted subjects in one study experienced ED or low libido with partners, but not with porn: all stated that internet porn use caused their ED/low libido.
  7. Enhanced attentional bias comparable to drug users. Indicates sensitization (a product of DeltaFosb).
  8. Greater wanting & craving for porn, but not greater liking. This aligns with the accepted model of addiction - incentive sensitization.
  9. Porn addicts have greater preference for sexual novelty yet their brains habituated faster to sexual images. Not pre-existing.
  10. The younger the porn users the greater the cue-induced reactivity in the reward center.
  11. Higher EEG (P300) readings when porn users were exposed to porn cues (which occurs in other addictions).
  12. Less desire for sex with a person correlating with greater cue-reactivity to porn images.
  13. More porn use correlated with lower LPP amplitude when briefly viewing sexual photos: indicates habituation or desensitization.
  14. Dysfunctional HPA axis and altered brain stress circuits, which occurs in drug addictions (and greater amygdala volume, which is associated with chronic social stress).
  15. Epigenetic changes on genes central to the human stress response and closely associated with addiction.
  16. Higher levels of Tumor Necrosis Factor (TNF) - which also occurs in drug abuse and addiction.

Articles listing relevant studies and debunking misinformation: