Is sex addiction real? That is, is it really a disorder, involving diminished control over behaviour?
Questions such as these are difficult to answer because it's always difficult to distinguish diminished capacity to resist a temptation from a diminished motivation to resist. People who tell us they literally can't resist might be deceiving themselves, or they might be looking for a convenient excuse.
There are two ways we can attempt to discover whether people who say that they can't control their behaviour really are suffering from some kind of diminished capacity.
First, we can gather as much behavioural evidence as possible: with enough evidence, we might be able to build an overwhelming case that a group of people genuinely suffer from diminished capacity.
When we see the costs – social, financial, physical and psychological – that drug addicts pay to continue using, we have good reason to think they have a diminished capacity to resist.
The second way we can proceed is to use scientific evidence that bypasses people's reports about what they can and can't do. Again, the case of drug addiction is a good example: some of the neurological changes in the brain of addicts seem to be changes in areas involved in self-control.
What about sex?
Recently, a group of researchers at UCLA attempted to resolve the question whether sex addiction is genuinely an addiction, utilising the second method.
Using EEG, which measures electrical activity on the surface of the brain, they determined that people who met the diagnostic criteria for "hypersexuality" did not find sexual stimuli any more compelling than did control subjects.
This is unlike the response seen in drug addicts, who find drug-related stimuli much more attention-grabbing than do unaddicted controls.
This research has been interpreted as showing that sex addiction isn't real. In the terms I used above, it might be taken to show that purported sex addicts do not lack the capacity to control their behaviour.
They simply lack the motivation; they might be morally condemned (if they are harming their families, say) rather than given a medical excuse.
But we shouldn't place too much weight on this study. The researchers looked for a likely correlate of a difficulty controlling behaviour, but there are many others possible correlates.
All we can conclude from the study is that sex addiction is different from drug addiction, not that it isn't real. Much more evidence is needed before we conclude that there is no diminished control.
Neuroscientists know a great deal about the mechanisms involved in control, attention regulation and conflict management. Most of these mechanisms are better studied with other methods, such as functional brain imaging, than with EEG (which was used in the study).
Before we conclude that sex addicts have no impairment in their capacities, we should conduct appropriate studies using these methods.
Addiction on the mind
Still, there are reasons to be sceptical that sex addiction will turn out to be an addiction that's anything as powerful as drug addiction. Drug addiction is so intractable in part because our brains are not designed to cope with drugs' pharmacological action.
There's evidence that addictive drugs drive up a dopamine value signal artificially, every time they are ingested. This makes it impossible for the brain to assign the appropriate value to the actual rewards drugs deliver.
As an aside, gambling may also cause a dysfunction in the dopamine system by delivering rewards in an unpredictable manner that's wildly different from the reward schedule our brains evolved to predict and understand.
That's how addicts can find themselves wanting a drug much more than they really like it.
Sex isn't like that: it's powerfully rewarding but the reward is one that our brains were designed to seek. For that reason, it's unlikely that the rewards of sex would ever become pathological in the way or to the degree that drugs can.
And anyway, addictions are diseases of persons, not brains.
Some people may genuinely experience a diminished capacity with regard to control over their sexual desires, even if there's no evidence that they lack the neural capacity for control. They might lack requisite skills, for reasons to do with their learning history or psychological history.
Not all self-control problems are best understood as neural problems: well-functioning brains can drive pathological behaviour. The recent research is one more piece of evidence, but the jury remains out on whether sex addiction is real.