Does porn destroy dopamine receptors?

Question

Kevin Majeres, a psychiatrist claims that porn destroys dopamine receptors. A quote from his website:

This is why pornography causes a vicious circle. When someone views pornography, he gets overstimulated by dopamine; so his brain destroys some dopamine receptors. This makes him feel depleted, so he goes back to pornography, but, having fewer dopamine receptors, this time it requires more to get the same dopamine thrill; but this causes his brain to destroy more receptors; so he feels an even greater need for pornography to stimulate him.

Source: http://www.purityispossible.com/the-science-behind-pornography/

Answer 1

No, or, at least, there is no evidence that it does.

The first problem with this is the source - obviously a site like "purityispossible.com" is going to have a moral agenda, and is going to be decidedly anti-pornography. As such, we would certainly, while not dismissing the possibility, ask that they offer research to back up their claims.

The next problem is referring to porn, love of chocolate, use of marijuana, listening to Taylor Swift songs, having sex with golf groupies (Tiger Woods' claimed addiction) as "addiction." While there might be some similar mechanisms involved in things we have trouble controlling our impulses for, the use of "addiction" as a much broader umbrella of behaviors, as opposed to the traditional "physical" addiction (body develops a physical tolerance, leading to increased dosages to achieve effect, and also leading to physical dependency and withdrawal when the substance is not available..... so the subject actually needing the substance, not just wanting or preferring) causes people to incorrectly over-equate the very different processes at work. This sets the stage for false equivalence.

In this case, here's a transcript from an online Q&A where someone asked a retired neurologist about "porn addiction" -

Okay, well the theoretical premise proposed by this science lecturer is nothing more than the application of the well-known and studied neurological basis for drug addiction upon porn addiction which unfortunately is entirely unsupported by scientific fact with regard to the latter.

A retired neurologists opinion | Your Brain Rebalanced

Furthermore, the claim that dopamine is an "addictive rewarding neurochemical" is not an accurate claim.

This article addresses the claims of dopamine behind all these different "behavior addictions," which is not accepted science, and what dopamine does and does not. The entire article is relevant to this discussion, BTW (bold emphasis mine) -

Dopamine serves many complex functions in the brain, and and only kindergarten brain science describes it as an addictive drug.

Dopamine is connected to rewarding experiences, but not in that it makes you feel good....Dopamine's role here is NOT that it makes you feel good. It doesn't - ...... Dopamine's role in pleasure and reward is it helps your brain to recognize "incentive salience".... A critical issue here is that a lack of dopamine doesn't actually make the experience feel less good.

No, Dopamine is Not Addictive | Psychology Today

The scientists in the field do not agree with the claims, either, when responding to papers or editorials offered in journals -

... Hilton and Watts offer some interesting neuroscience perspectives on their conceptualization of pornography problems as an addictive disorder.... Hilton and Watts offered little, if any convincing evidence to support their perspectives.... Instead, excessive liberties and misleading interpretations of neuroscience research are used to assert that excessive pornography consumption causes brain damage..... Depending on how addiction is defined, this is either well supported.... or whole speculative as in the case of pornography consumption.

Neuroscience research fails to support claims that excessive pornography consumption causes brain damage | Surgical Neurology International

It appears that the claims are based on false equivalence and poor, misleading interpretations of the science.

Answer 2

Yes, it surely does. The more accurate term for this would be the downregulation of dopamine receptors. It might not be as extreme as, for instance, cocaine addiction, but watching porn does affect the brain. In fact, many drugs hijack the same reward circuits that were evolved for reproduction, that's why they are so addictive:

The human brain is programmed to incentivize behaviors that contribute to survival. The mesolimbic dopaminergic system rewards eating and sexuality with powerful pleasure incentives. Cocaine, opioids, alcohol, and other drugs subvert, or hijack, these pleasure systems, and cause the brain to think a drug high is necessary to survive. [emphasis added] Evidence is now strong that natural rewards such as food and sex affect the reward systems in the same way drugs affect them, thus the current interest in ‘natural addiction.’ ...

Can Pornography Use Become An Actual Brain Addiction? (2011)

You can find numerous evidence that porn does cause the downregulation, but most studies do not isolate porn and instead focus on so called Internet addiction, which I think actually describe the cause of porn usage and not the Internet usage itself for the most part:

An increasing amount of research has suggested that Internet addiction is associated with abnormalities in the dopaminergic brain system. We hypothesized that Internet addiction would be associated with reduced levels of dopaminergic receptor availability in the striatum compared with controls. To test this hypothesis, a radiolabeled ligand [C]raclopride and positron emission tomography was used to assess dopamine D2 receptor binding potential in men with and without Internet addiction. Consistent with our prediction, individuals with Internet addiction showed reduced levels of dopamine D2 receptor availability in subdivisions of the striatum including the bilateral dorsal caudate and right putamen. This finding contributes to the understanding of neurobiological mechanism of Internet addiction.

Reduced striatal dopamine D2 receptors in people with Internet addiction

There are more recent studies that cover porn addiction specifically:

In a recent study by our group, we recruited healthy male participants and associated their self-reported hours spent with pornographic material with their fMRI response to sexual pictures as well as with their brain morphology (Kuhn & Gallinat, 2014). The more hours participants reported consuming pornography, the smaller the BOLD response in left putamen in response to sexual images. Moreover, we found that more hours spent watching pornography was associated with smaller gray matter volume in the striatum, more precisely in the right caudate reaching into the ventral putamen. [emphasis added] We speculate that the brain structural volume deficit may reflect the results of tolerance after desensitization to sexual stimuli.

Neurobiological Basis of Hypersexuality (2016)

And for those who want to know more about porn addiction in general, here's the link to many studies that describe this phenomenon:

There are no scientific studies that say porn is addictive, right?

Answer 3

Some recent research not highlighted in the accepted answer backs it up even more, quoting a popsci summary of if:

In research invited for submission to the journal Socioaffective Neuroscience of Psychology, authors Steele, Staley, Fong and Prause used EEG testing to examine the effects of visual erotica, on the brains of people who felt they had problems controlling their porn use. 52 sex addicts, including men and women, had their brain’s electrical activity examined while they looked at erotic imagery. Sex addiction theory predicts that these individuals would show brain patterns consistent with that of cocaine addicts, who demonstrate specific electrical changes in the brain’s activity, in response to drug-related cues. Sex addiction proponents, from Rob Weiss to Carnes have long argued that sex and porn are “like cocaine” in the brain.

But, when EEG’s were administered to these individuals, as they viewed erotic stimuli, results were surprising, and not at all consistent with sex addiction theory. If viewing pornography actually was habituating (or desensitizing), like drugs are, then viewing pornography would have a diminished electrical response in the brain. In fact, in these results, there was no such response. Instead, the participants’ overall demonstrated increased electrical brain responses to the erotic imagery they were shown, just like the brains of “normal people” as has been shown in hundreds of studies.

So if porn is addictive, it's not in the same way as cocaine etc., at least as far as EEG measures are concerned. The actual paper is also free in PMC.

The caveat to all such porn studies is that they have been surprisingly few in number.

Also hypersexuality is more often treated off-label (because there are no FDA-approved drugs for it) with SSRIs, which increase serotonin, rather than with drugs acting directly on dopamine, although naltrexone (an antagonist of the opioid receptor, so at least having something to do with addiction) has been also been tried. But there's not much in the way of studies of that either, and an effort to include hypersexuality in DSM-5 failed.

Perhaps the main pharmacological indicator that dopamine is somehow implicated comes from medicated patients with Parkinson's disease; some develop hypersexuality (and quite a few other behavioral issues like excessive gambling) as a side-effect of being treated with L-dopa, a dopamine precursor that turns into actual dopamine in the brain. However, fairly recent (2012) research indicates that at the usual therapeutic doses L-dopa does nothing of the sort in healthy volunteers. Testing higher doses "will be difficult, though, since higher doses of all currently available drugs that selectively augment DA neurotransmission are limited by side effects such as nausea, vomiting, dizziness and drowsiness."

One very recent (2017) Polish fMRI study found that

men with and without PPU [= problematic pornography use] do not differ in striatal reactivity and hedonic values either for erotic or monetary rewards. The key difference between these two groups is in striatal reactivity (and accompanying behavioral reactions) in response for cues.

So (amusingly) yourbrainonporn turned out just the same for all, yourbrainanticipatingporn is different for some. Although this may sound reassuring, the wanting-difference part is however consistent with the incetive salience theory of addiction.

So the (addiction) question may come down to whether you think behavioral issues like gambling disorder are (or aren't) addiction. I note that the accepted answer implies that behavioral addictions aren't addictions, but this is not the prevailing opinion in the DSM-5, which recategorized gambling disorder from an impulse control disorder to an addiction. There's even an official blurb about this in their change summary

An important departure from past diagnostic manuals is that the substance-related disorders chapter has been expanded to include gambling disorder. This change reflects the increasing and consistent evidence that some behaviors, such as gambling, activate the brain reward system with effects similar to those of drugs of abuse and that gambling disorder symptoms resemble substance use disorders to a certain extent.

The reason why the other proposed behavioral addictions didn't get included was the lack of enough empirical evidence in their favor as such. (Internet gaming disorder was included in the "for future research" section with a passing mention that it might rise to the level of an addiction in some extreme cases.)

Anyway, here's a table with the Polish study participants' other group characteristics:

(I snipped some of the really long and boring methodological footnotes.)

One interesting (but rather obvious) fact is that more porn correlated with more masturbations. It's not at all clear what's the cause and what the effect though. Do they watch more porn because they want to masturbate more, or is it the other way around, i.e. watching more porn turns them on so they masturbate more? In other words, is PPU just the low-hanging-fruit manifestation of hypersexuality or is it really an addiction to porn? As the song goes, more research is needed.