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Last September I reviewed a documentary called 'Porn on the Brain'. It was the kind of edgy programme you’d expect from Channel Four – a combination of British tongue-in-cheekery, outrageous punditry, and bona fide science. Overall it succeeded by raising questions about the kind of research we need in order to understand compulsive sexual behaviours and to help people overcome them.
The scientific centrepiece of Porn on the Brain was the research of Cambridge University neuropsychiatrist, Dr Valerie Voon. At the time of screening, Voon was conducting a study to test whether compulsive sexual behaviour – including viewing pornography – alters brain activity in a similar way to drug dependence and other recognised addictions. Now, nine months later, this research has been published in the journal PLOS ONE.
Using functional magnetic resonance imaging, Voon and her team compared the brain response triggered by pornographic videos between two groups of men: those diagnosed with compulsive sexual behaviour disorder (CSB) and a group of healthy controls. To be diagnosed with CSB, the men completed a detailed questionnaire and psychiatric interview, with a particular focus on how often they viewed online pornography. Of their time online, the CSB group reported spending 25% viewing porn, more than five times that of the control group. They also reported more problems maintaining jobs and intimate personal relationships.
Turning to the neuroimaging, what Voon found was intriguing albeit preliminary. In both groups of men, videos depicting explicit sex activated brain regions that are linked with processing of reward and emotion, many of which are abnormally activated in drug addiction. In the CSB group, especially, these regions were more strongly activated by porn and more tightly coupled with feelings of sexual desire. The upshot of Voon’s study is that there could be a shared brain network associated with many compulsive disorders, regardless of whether they involve consumption of drugs or more 'natural' rewards such as sex.
Do these results mean that compulsive viewing of pornography is an addiction like dependence on cocaine or heroine? No, and Voon is keen to emphasise this point in both the published article and the press release issued by Cambridge University. Addiction can’t be diagnosed with a brain scan, and even if it could, we still don’t know enough about CSB for it to be recognised as an addiction in mainstream psychiatry.
Do the results tell us that online pornography itself is addictive like a drug? No. Do they say anything at all about the non-compulsive viewing of pornography? No. Do they allow us to conclude that pornography “damages” or “changes” the brain in any harmful way? No. Do they even translate to all sufferers of CSB? No – the study tested a small sample of men only and, in any case, we can never draw strong conclusions from a single study alone.
The results don’t even mean that the brain networks activated by pornography in men with CSB are necessarily the cause of their compulsive behaviour. Why? Because the study measured which brain activity correlated with CSB, and correlation does not imply causation. To show that any given brain area is causally involved in CSB, we would need to perturb activity in that area, for instance using electrical stimulation or pharmacology, and then show that the compulsion to view pornography was reduced or altered in some way.
What I found particularly impressive about this study is that all of these caveats are highlighted by Voon herself, providing a master class on how to tackle a controversial topic with confident transparency. And none of the limitations take away from what the study sought to discover in the first place – whether CSB is associated with a similar profile of abnormal brain activity to drug addiction.
Too often we see scientific discoveries about impulse control hijacked by political or moral noise. With a wave of the wand, evidence-based discussions about pornography can disappear amidst arguments that porn is morally corrupting or that addiction itself is a failure of moral fibre. Science cares little for our moral vicissitudes but it perks up when there is evidence that a compulsion causes demonstrable harm. And this is why Voon’s study is important - because it sheds light on a corner of human behaviour that is shrouded in ignorance and taboo. Only with a deep knowledge of the underlying neurobiology can we hope to develop the most effective treatments for compulsive sexual behaviour and related disorders of control.
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