Desensitization: A Numbed Pleasure Response
Desensitization is just one of many brain changes caused by addiction. A few other major brain changes include;
- Sensitization: Formation of Pavlovian memory circuits related to the addiction
- Hypofrontality: Weakening of the impulse control circuits.
- Dysfunctional stress circuits - Stress will easily trigger a relapase
- If you haven't already, I strongly suggest watching Your Brain on Porn: Porn Addiction, as it covers desensitization.
- Intoxicating Behaviors: 300 Vaginas = A Lot of Dopamine, Protect Your Appetite for Pleasure and Has Evolution Trained Our Brains to Gorge on Food and Sex? are our best articles on dopamine receptors and desensitization.
- Porn Then and Now: Welcome to Brain Training and Porn, Novelty, and the Coolidge effect explain how today's Internet porn can cause desensitization.
The neurotransmitter dopamine is the gas that powers our reward circuitry, and it is behind motivation, reward, desires, cravings, and of course, libido and erections. The level of dopamine signalling correlates to feelings of pleasure in human studies. Dopamine is the main player in reward and addiction, and the key to understanding desensitization.
- Short YouTube video on dopamine and reward. Another on downregulation of dopamine receptors
- Easy-to-understand Psychology Today article explaining how dopamine functions in our everyday lives.
- Videos by addiction researchers Nora Volkow (NIDA director) and Adam Kepecs explaining dopamine.
A numbed pleasure response, or desensitization, is probably the best understood brain change that addiction induces. (There is another addiction-related brain change known as "sensitization." Here's an explanation that contrasts desensitization with sensitization). The main physiological feature of reward circuitry desensitization is a decline in dopamine signaling. Desensitization seems to be caused by a number of factors, including:
- Decline in dopamine (D2) receptors. Fewer D2 receptors mean less sensitivity to available dopamine, which leaves the addict less sensitive to the pleasure normally found in experiences.
- Decline in baseline (tonic) dopamine levels. Lower dopamine levels leave an addict "hungry" for dopamine-raising activities/substances of all kinds.
- Blunted dopamine in response to normal rewards. Dopamine normally rises in response to rewarding activities. Once your addiction is the most reliable source of dopamine, cravings arise urging you to use porn.
- Decline in CRF-1 receptors, which function to raise dopamine levels in the striatum (only studied with cocaine)
- Loss of reward circuit grey matter, which means a loss in dendrites. This translates into fewer nerve connections or synapses. A 2014 study on porn users correlated less grey matter with more porn use.
- Decline in opioids or opioid receptors
Both #2 and #3 may involve increased dynorphin which inhibits dopamine, and weakening of certain pathways (glutamate) conveying messages to the reward circuitry, In other words desensitization is rather complex, and an awful lot is left to learn.
What causes desensitization?
Too much of a good thing.
Dopamine is where it all starts. If dopamine is too high for too long it leads to nerve cells losing their sensitivity. If someone continues to scream, you cover your ears. When dopamine-sending nerve cells keep pumping out dopamine, the receiving nerve cells cover their "ears" by reducing dopamine (D2) receptors. (See: Volkow May Have Uncovered Answer to Addiction Riddle.)
- The desensitization process can begin fairly quickly, even with natural rewards such as junk food. How quickly it occurs depends on the intensity of use and the vulnerability of the brain.
- How much is too much is determined by brain changes - not by outward behaviors, such as the amount of drug used, calories consumed, or time spent watching porn. No two people are alike.
- Abnormally high dopamine levels are not necessary to cause desensitization. Smoking hooks a far greater percentage of users than cocaine, even though cocaine furnishes a bigger neurochemical blast. Many small hits of dopamine can train the brain more thoroughly than fewer, more intense hits.
- Nor do dopamine levels need to be continuously elevated to cause desensitization. Compare overeating and becoming obese to cigarette smoking. Both produce down regulation of dopamine receptors, but far less time is spent eating than puffing.
- Overriding natural satiation mechanisms may be a key factor in how natural reinforcers trigger desensitization. Overeating and heavy porn users ignore 'stop' signals, or more accurately their addicted brains no longer experience "satisfaction," so they keep on consuming (see - Men: Does Frequent Ejaculation Cause A Hangover?)
Desensitization is behind tolerance, which is the need for greater and greater stimulation to experience the same "high." Porn users often escalate to new genres as way to jack up their lagging dopamine. Novelty and violated expectations (surprise) increase dopamine.
This is not a theoretical discussion of desensitization, as three recent Internet addiction brain studies assessed dopamine signalling in Internet addicts. Each measured different aspects of desensitization and found significant difference between Internet addicts and controls. In study #2, it specifically states - "watching online pornographies or adult movies".
- Reduced Striatal Dopamine D2 Receptors in People With Internet Addiction (2011)
- Reduced Striatal Dopamine Transporters in People with Internet Addiction Disorder (2012)
- PET imaging reveals brain functional changes in internet gaming disorder (2014)
In this study on porn users - Brain Structure and Functional Connectivity Associated With Pornography Consumption: The Brain on Porn (2014) - experts at Germany's Max Planck Institute found that higher hours per week & more years of porn viewing correlated with a reduction in grey matter in sections of the reward circuitry involved in motivation and decision-making. Reduced grey matter in this reward-related region means fewer nerve connections. Fewer nerve connections here translates into sluggish reward activity, or a numbed pleasure response. The researchers interpreted this as an indication of the effects of longer-term porn exposure.
- Lead author Simone Kühn said - "That could mean that regular consumption of pornography more or less wears out your reward system."
Summary: When dopamine receptors drop after too much stimulation, the brain doesn't respond as much, and we feel less reward from pleasure. That drives us to search even harder for feelings of satisfaction—for example, by seeking out more extreme sexual stimuli, longer porn sessions, or more frequent porn viewing - thus further numbing the brain.
Desensitization versus habituation:
Habituation is a temporary decline or cessation of dopamine release in response to one specific stimulus. This is a normal process and can change moment to moment. Desensitization refers to long-term changes involving a decline in dopamine signaling and D2 receptors. This is an addiction process and may take months to years to develop, and a long time to reverse.
Dopamine levels spike throughout the day in response to anything we find rewarding, novel, enjoyable, interesting, even frightening or stressful. The main message of dopamine is - "this is important, pay attention, and remember it."
Let's use eating as an example. When one is hungry, dopamine rises in anticipation of taking that first bite of a burger. As lunch continues, dopamine declines and we become habituated. No further spikes in dopamine signals means, "I've had enough." You may not want anymore burger, but if you are offered a chocolate brownie, your dopamine spikes, which urges you to override normal satiation mechanisms and have some.
Another example might have you flipping through pictures of your friend's trip to the Grand Canyon. You may receive a little spike of dopamine with each picture, but you quickly habituate and move to the next picture. Same thing might occur when clicking through pictures of Sport Illustrated swimsuit models. You linger on certain pictures (slow habituation), but not so with other pictures (fast habituation).
If I'm desensitized don't I need to avoid dopamine-elevating activities?
This is a logical question as all rewards share some overlapping brain structures. For example, if your brain is desensitized due to alcoholism or cocaine addiction, your chances of erectile dysfunction increase and libido generally decreases. That tells us overlap in brain circuitry exists. However, experience informs us that drinking wine, eating chocolate and having sex are different, which means each stimulus involves unique pathways in addition to the overlap.
Recent research found that sex activates it's own set of reward circuit nerve cells. Surprisingly cocaine & methamphetamine activates the exact same nerve cells in the reward center as do sexual rewards. In contrast, there's only a small percentage of nerve-cell activation overlap between meth and food or water (other natural rewards).
Additional research found that ejaculation in male rats can shrink the reward circuit nerve cells that produce dopamine. This normal event mimics the effects of heroin addiction on these same dopamine nerve cells. This doesn't mean sex is bad. It simply informs us that addictive drugs hijack the exact same mechanisms that urge us back into the bedroom for a romp.
Put simply, addictive drugs like meth & heroin are compelling because they hijack the precise nerve cells and mechanisms, which evolved to make sex compelling. Most other pleasures do not. Thus, the familiar "talking point" that "Everything raises dopamine. Golf or laughing are certainly not addictive, and how different can they be from internet porn in terms of dopamine increases?" falls apart.
You can't avoid dopamine-raising activities, nor should you. Normal everyday activities, and maybe even some alcohol and pot, shouldn't cause a problem. Sure, it would be great if you could stop all drugs, smoking, caffeine and eat really healthily, but men have recovered while still imbibing now and then.
It's great to engage in natural rewards, such as kissing, cuddling, music, dancing, exercise, sports, good food, socializing, etc. Besides raising dopamine, most of these activities also rise oxytocin levels. Oxytocin is unique in that it both activates the reward circuit and decreases cravings. The bottom line is simple: Avoid what got you into this mess. I strongly suggest reading this FAQ: What stimuli must I avoid during my reboot?
What can I do to speed recovery?
A common question is: "What supplement or food will speed the return of dopamine receptors?" Your addiction was not caused by a nutritional deficiency, so it won't be corrected by a supplement. Dopamine receptors are proteins made from the same amino acids found in every one of your cells. Desensitization is caused by too much stimulation, not too few amino acids. If they wanted to, your nerve cells could rebuild the dopamine receptors in a few hours.
More importantly, desensitization involves multiple links in the reward chain undergoing alteration, which results in lower dopamine signalling (dopamine receptors & dopamine levels). You may have plenty gas (dopamine) in your tank, but your fuel pump is broken and half your spark plugs are missing. Adding more gas will do nothing to solve your problem.
Articles covering what to eat to raise dopamine levels are largely nonsense. First, L-tyrosine (often recommended) is the precursor for dopamine (and a few other important hormones). It is easily obtained in a normal diet. Second, "dopamine-containing foods" are of no value as dopamine doesn't cross the blood-brain barrier—meaning that what you put in your stomach won't help stabilize dopamine levels in your brain. Third, and most important, desensitization is primarily caused by a decline in dopamine (D2) receptors and changes in synpases. (For suggestions of those recovering see Supplements.)
What you can do is exercise and meditate. Aerobic exercise is the one thing that increases both dopamine and dopamine receptors. Exercise also reduces cravings and eases depression. One study reports that meditation increases dopamine a whopping 65%. Another study found far more frontal cortex gray matter in long-term meditators. Addictions cause a decrease in frontal cortex gray matter, which is associated with desensitization and less dopamine making it to the frontal lobes. Less gray matter is called hypofrontality, and correlates with poor impulse control.
[27 days without any PMO] "Here are the changes brought about in my own life from the "rebooting" process: The results are 100% real and palpable, and they permeate all aspects of my life. Without the PMO zombifying trance, I've been more comfortable in my own skin, and it seems it's been of great help in interactions with the opposite sex. I also get excited because so many other people have noticed the same effects: increased sexual attractiveness to women in more subtle situations, and increased desire to read and give responses to their cues. Also increased desire to socialize, and newfound confidence. This is no placebo effect, and for any skeptics; the only way to be convinced is to try it. You'll see."