The suspect "null results" explanatory trend

Printer-friendly version

Bad scienceTo date, researchers have investigated few of the variables that might predict youthful porn-related sexual dysfunctions in healthy young men, such as percentage of internet porn-assisted versus porn-free masturbation, ratio of ejaculations with a real partners to ejaculations with internet sexually explicit material (iSEM), degree of escalation to new genres of iSEM, years of iSEM use, whether iSEM use began prior to puberty, lifetime quantity and trend of iSEM use, the presence of cybersex addiction or hypersexuality, and so forth.

However, sexologists searching for easy ways to discover (or "disprove") iSEM's possible role in youthful sexual dysfunctions are publishing studies that claims to find no correlation between sexual dysfunction rates and narrow aspects of iSEM use, such as "hours of weekly use in the past month" and "frequency of use in the last year".

Before examining their results, it is worth noting that research on cybersex addiction is showing that hours and frequency of use do not predict problems as accurately as other factors, such as degree of sexual arousal, number of internet sex applications opened, coping by sexual behaviors, and psychological symptoms (Brand et al., 2011, Laier et al., 2015). In a similar vain, Internet addiction disorders are more related to passion and motivations for play than to hours of use (Kneer & Rieger, 2015). It appears that brains differ in how much stimulation they can tolerate, such that null results of linear correlations between amount of use and youthful sexual dysfunctions likely tell us very little of value. They certainly don't "prove" internet porn is not the culprit in youthful ED, as their authors boldly claim.

The first of these null results papers (critiqued more fully here) relied on data from 4 older studies, which had nothing to do with erectile functioning. It analyzed subjects, average age 23, and claimed to compare their weekly hours of iSEM viewing to a number in response to a single question about "sexual arousal" after viewing visual sexual stimuli (Prause & Pfaus, 2015). Arousal was not assessed via sexual responsiveness, erections, or brain activation. Subjects in the 2+ hours per week porn use had slightly higher arousal scores after viewing, but this revealed nothing about their erectile health or sexual performance with a partner.

A smaller number of subjects also took the International Index of Erectile Function questionnaire (IIEF-6), the average results of which indicated that they suffered from ED (a score of 21.4 out of 30). Oddly, the researchers published no IIEF data in relation to viewing hours.

Subjects who viewed more iSEM also reported slightly higher desire for masturbation and sex with "a partner." (Many were without partners, however, and may have been rating their desire for sex with their favorite pornstar.) It is common for heavy iSEM users to have increased cravings for sexual stimulation. However, cravings do not necessarily translate into better sexual performance, as seen in Voon et al., in which the majority of subjects reported libido and erectile problems with real partners but not with iSEM.

Nevertheless, based on these ambiguous and incomplete results, and despite the evidence that their youthful subjects actually had ED, the authors widely promoted a press release suggesting that iSEM use enhances sexual performance: "Can watching porn make you better in bed?" (Concordia University - Montreal, press release, 2015). Their paper has been criticized in a peer-reviewed journal for both extensive discrepancies and unsupported conclusions, and its failure to investigate critical parameters such as total iSEM usage, age iSEM use began, escalation to more extreme material, and extent of sexual activity (Isenberg, 2015).

A second 2015 paper (critiqued more fully here) looked at frequency of iSEM use in the last year in relation to ED rates in men from Norway, Portugal and Croatia (Landripet & Štulhofer, 2015). Researchers excluded men who had not had sex in the past 12 months. (Interestingly, a 1999 cross-sectional study found that sexual dysfunction rates are considerably higher when all men in an age group are included, rather than just those who have been sexually active with partners in the past year (Laumann et al., 1999).)

In this paper, men 18-40 reported ED rates as high as 31% and rates of "low sexual desire" as high as 37%. In comparison, earlier research by one of the authors reported ED rates in men 35-39 of only 5.8% in 2004 (Štulhofer & Bajić, 2006). Yet the paper's abstract does not mention the alarming dysfunction rates.

Instead, the authors reassure readers that, contrary to rising public concerns, iSEM does not seem to be a significant risk factor for youthful sexual dysfunction. That seems overly definitive, given that the Portuguese men surveyed, who reported using much less iSEM than Norwegians, also reported much lower rates of ED. This paper, too, has been formally criticized for failing to employ comprehensive models able to encompass both direct and indirect relationships between variables known or hypothesized to be at work (Hald, 2015).

Impartial research by physicians and other experts with proficiency in the study of the neural substrates governing arousal and erection is needed to assess the possibility of porn-related sexual dysfunctions. In the interim, researchers and those who rely on them for information, are cautioned to avoid inadequately supported conclusions, misleading analysis, and overstated research headlines, which appear to reflect an underlying agenda that is anything but scientific and may even signal a broken peer-review process in the sexology field.

Also see: Research confirms sharp rise in youthful ED


  1. Brand, M., Laier, C., Pawlikowski, M., Schächtle, U., Schöler, T., & Altstötter-Gleich, C. (2011). Watching pornographic pictures on the Internet: role of sexual arousal ratings and psychological-psychiatric symptoms for using Internet sex sites excessively. Cyberpsychology, Behavior and Social Networking, 14(6), 371–377.
  2. Laier C, Pekal J, Brand M, (2015). Sexual Excitability and Dysfunctional Coping Determine Cybersex Addiction in Homosexual Males. Cyberpsychol Behav Soc Netw. 2015 Oct;18(10):575-80. doi: 10.1089/cyber.2015.0152.
  3. Kneer, J., & Rieger, D. (2015). Problematic Game Play: The Diagnostic Value of Playing Motives, Passion, and Playing Time in Men. Behavioral Sciences, 5(2), 203–213.
  4. Prause, N., & Pfaus, J. (2015). Viewing Sexual Stimuli Associated with Greater Sexual Responsiveness, Not Erectile Dysfunction. Sexual Medicine, 3(2), 90–98.
  5. Voon, V., Mole, T. B., Banca, P., Porter, L., Morris, L., Mitchell, S., … Irvine, M. (2014). Neural Correlates of Sexual Cue Reactivity in Individuals with and without Compulsive Sexual Behaviours. PLoS ONE, 9(7), e102419.
  6. Concordia University - Montreal, press release. (2015, March 16). Can watching porn make you better in bed? ( Retrieved July 23, 2015, from
  7. Isenberg, R. A. (2015). Viewing Sexual Stimuli Associated with Greater Sexual Responsiveness, Not Erectile Dysfunction: A Comment. Sexual Medicine, n/a–n/a.
  8. Landripet, I., & Štulhofer, A. (2015). Is Pornography Use Associated with Sexual Difficulties and Dysfunctions among Younger Heterosexual Men? The Journal of Sexual Medicine, 12(5), 1136–1139.
  9. Laumann, E. O., Paik, A., & Rosen, R. C. (1999). Sexual dysfunction in the United States: prevalence and predictors. JAMA, 281(6), 537–544.
  10. Štulhofer, A., & Bajić, Ž. (2006). Prevalence of Erectile and Ejaculatory Difficulties among Men in Croatia. Croatian Medical Journal, 47(1), 114–124.
  11. Hald, G. M. (2015). Comment on: Is Pornography Use Associated with Sexual Difficulties and Dysfunctions among Younger Heterosexual Men? The Journal of Sexual Medicine, 12(5), 1140–1141.