Watching Internet porn will wear out your brain and make it shrivel (first brain scan study published on porn users), 5/28/2014

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JAMA Psychiatry logoIf you watch a lot of soft porn, you may want more extreme stuff in the future. Porn, suggests a new study, influences the structure of your brain: in fact, it might even make your brain shrink.

Men who watch large amounts of sexually explicit material have brains with smaller reward systems, a study finds.

"That could mean that regular consumption of pornography more or less wears out your reward system," says Simone Kühn, psychologist at the Max Planck Institute for Human Development in Berlin and lead author of the study, published in the "JAMA Psychiatry" journal.

Your reward system is a collection of neural structures in the brain that regulate and control behavior by inducing pleasure.

The researchers scanned the brains of 64 men aged between 21 and 45 with a MRI machine.

Those probands - or study subjects - who watched porn often had a smaller striatum, which is an important part of the reward system and also involved in sexual arousal.

The study also found that the reward systems of porn-experienced men were less active when they watched sexually arousing pictures inside the MRI machine.

"We assume that probands with a high porn consumption need increasing stimulation to receive the same amount of reward," Simone Kühn says.

Consequence or precondition?

But were men with smaller striatum seeking more porn because they needed more external stimulation, or did the higher consumption of porn make this part of the brain smaller?

The researchers admit both could be true. But they say the latter is more likely.

Kühn says existing psychological, scientific literature suggests consumers of porn will seek material with novel and more extreme sex games.

"That would fit perfectly the hypothesis that their reward systems need growing stimulation."

A brain scan can reveal a lot.

In future studies the researchers plan to observe brain changes in study subjects over a period of time to see whether the reward system really changes with increasing porn consumption.

Like cocaine and gaming

Kühn says the team had predicted it would observe changes in the reward system - but the opposite of what it ultimately found.

The striatum is also involved in drug addiction.

In 2001, researchers found that reward-system-related brain parts were up to ten percent larger in cocaine addicts than in non-dependent probands.

And as if that wasn't enough: "In a study with teenagers we found that frequent PC games playing leads to an increase in the size of the striatum," says Kühn. But she notes she was surprised to see that male porn-watchers had smaller - not larger - striatum than the other men in the study.

She says she had expected porn consumption to increase the size of the reward system - rather than make it shrink.

Is porn addiction real?

"Pornography is no longer an issue of minority populations but a mass phenomenon that influences our society," the researchers write in the journal, adding that an estimated 50 percent of all Internet traffic is related to sex.

Psychiatrists have been debating whether it is possible to develop an addiction to porn. But they have yet to even agree on a clinical definition of pornography addiction.

In February, psychiatrists wrote in "Current Sexual Health Reports" that there is no such thing as porn addiction. There was no sign, they wrote, that use of pornography causes any changes to the brain.

This latest research may change their minds.

JAMA Psychiatry, online May 28, 2014.

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THE ABSTRACT (FULL STUDY)

Brain Structure and Functional Connectivity Associated With Pornography Consumption. The Brain on Porn

Simone Kühn, PhD1; Jürgen Gallinat, PhD2,3
 
JAMA Psychiatry. Published online May 28, 2014. doi:10.1001/jamapsychiatry.2014.93
1Max Planck Institute for Human Development, Center for Lifespan Psychology, Berlin, Germany
2Clinic for Psychiatry and Psychotherapy, Charité University Medicine, St Hedwig-Krankenhaus, Berlin, Germany
3University Clinic Hamburg-Eppendorf, Clinic and Policlinic for Psychiatry and Psychotherapy, Hamburg, Germany

Importance  Since pornography appeared on the Internet, the accessibility, affordability, and anonymity of consuming visual sexual stimuli have increased and attracted millions of users. Based on the assumption that pornography consumption bears resemblance with reward-seeking behavior, novelty-seeking behavior, and addictive behavior, we hypothesized alterations of the frontostriatal network in frequent users.

Objective  To determine whether frequent pornography consumption is associated with the frontostriatal network.

Design, Setting, and Participants  Sixty-four healthy male adults with a broad range of pornography consumption at the Max Planck Institute for Human Development in Berlin, Germany, reported hours of pornography consumption per week. Pornography consumption was associated with neural structure, task-related activation, and functional resting-state connectivity.

Main Outcomes and Measures  Gray matter volume of the brain was measured by voxel-based morphometry and resting state functional connectivity was measured on 3-T magnetic resonance imaging scans.

Results  We found a significant negative association between reported pornography hours per week and gray matter volume in the right caudate (P  < .001, corrected for multiple comparisons) as well as with functional activity during a sexual cue–reactivity paradigm in the left putamen (P < .001). Functional connectivity of the right caudate to the left dorsolateral prefrontal cortex was negatively associated with hours of pornography consumption.

Conclusions and Relevance  The negative association of self-reported pornography consumption with the right striatum (caudate) volume, left striatum (putamen) activation during cue reactivity, and lower functional connectivity of the right caudate to the left dorsolateral prefrontal cortex could reflect change in neural plasticity as a consequence of an intense stimulation of the reward system, together with a lower top-down modulation of prefrontal cortical areas. Alternatively, it could be a precondition that makes pornography consumption more rewarding.


 

COMMENTS ON STUDY BY MD RESEARCHER, D.L. Hilton

Basically, this confirms what we predicted based on the neuromodulation data and our DNA work: that pornography as a powerful learning template would structurally alter reward systems.  This is a well designed, well executed study, and it  is published in JAMA, the Journal of the American Medical Association.

In their conclusion, the authors give support to pornography causing this neuroplastic change.  However, they appropriately state that because it is not a longitudinal study and is therefore correlative they can not affirm causation. In other words, did porn cause the changes, or were the changes already there and therefore those that watch porn did so because they were pre-programmed to do so?

They did not refer to any other neuroplasticity paper in their discussion, however, and that needs to be done.  I will add this to a paper I am currently  writing.

In the context of these other studies on structural change (which are longitudinal), the DeltaFosB work, and our DNA work from PNAS I think this is a compelling piece of the argument. This dovetails nicely with Dr. Voon's [Cambridge] soon to be published sensitization work.


 

[Comparison with Voon's upcoming study]

The new German study uses different tasks with brief static images of pornography (deliberately brief) compared to sports images and show decreased putaminal activity suggesting a role for desensitization correlating with degree of porn use in regular users of pornography.  [The Voon] study focuses on video clips which may be more engaging and motivating and studies a categorical diagnostic group who endorse having difficulties with use and control of the behaviour.  The findings are not incompatible as the populations and task design differ. 

[The German study looked at] the dorsolateral striatum (more involved in motor tasks and habits) whereas [the Cambridge study] focus is on the ventral striatum although dorsal anterior cingulate and amygdala are also crucial regions.