Opponents of a politician might use the label "sex addict" as a pejorative, indicating moral failure as well as a lack of willpower and therefore fitness to govern. Supporters, however, may use it as an apologia. In this view, sex addicts, like alcoholics, suffer from a disease that produces strong subconscious cravings, so they should be treated compassionately and given a shot at redemption.
Suspicion of the entire notion of sex addiction is understandable. Many wonder whether it's just an excuse concocted by philandering politicians and celebrity publicists to justify cheating or worse. After all, it's common these days to hear such usages as, "I'm addicted to Starbucks lattes/The Colbert Report/Christian Louboutin shoes." Those are clearly not true addictions, but rather mere habits or desires. Should claims of sex addiction be regarded as similarly unserious?
Fortunately, the neurobiology of pleasure offers part of the answer to this question. The emerging view is that sex addiction is a real disease of the brain, but that it affects only a small fraction of those - including politicians and celebrities - who are sexually dishonest.
As a key motivator in our lives, pleasure is central to learning. We must find such things as food, water, and sex rewarding in order to survive and pass our genetic material on to the next generation. Pleasing experiences evoke neural signals that converge on a small group of interconnected areas in the brain known as the medial forebrain pleasure circuit, in which the neurotransmitter dopamine plays a crucial role.
This dopamine-using pleasure circuitry can be co-opted by some psychoactive substances (those that tend to be addictive, such as cocaine, nicotine, heroin, and alcohol, but not those that don't, such as SSRI antidepressants and LSD). It's becoming clear that drug addiction involves long-lasting changes in the electrical, morphological, and biochemical functions of neurons and synaptic connections within the brain's pleasure circuit. Studies in laboratory animals indicate that these changes underlie many of the terrifying aspects of addiction, including tolerance (the need for successively larger doses), strong subconscious cravings, withdrawal, and relapse.
Human brain-imaging studies show that orgasm strongly activates this dopamine-using circuit in both men and women. Meanwhile, drugs that alter dopamine signaling in the brain can affect libido and orgasm. Furthermore, there are human genetic variants that affect dopamine signaling and increase the risk for drug addiction. These variants also tend to promote risky behavior generally, including compulsive sex.
If orgasms are a form of pleasure that carries a risk of addiction, they should produce changes in the pleasure circuit similar to those seen in drug addiction. While we don't yet know if this is actually the case, there is good reason to believe it is.
Unlike using heroin, however, having sex is a natural activity. Almost everyone has sex, and, of course, heterosexual intercourse is the traditional means of propagating the species.
So when does a normal, commonplace behavior become an addiction? Is the teenager making frequent use of online pornography a sex addict? The woman who never leaves the dance club alone? The businessman who seeks out prostitutes every time he travels?
Merely liking sex a lot does not make one a sex addict, and defining sex addiction is not always straightforward. But the fundamental criteria are not really different from those for drug and alcohol addiction, namely:
The behavior continues despite continued negative consequences to the addict and others.
The behavior seems necessary for the addict to "feel normal" and be able to face the typical stresses of life.
The addict repeatedly breaks promises to herself or others that she will quit.
The addict regrets the behavior.
For the few whose behavior meets these criteria, sex addiction is very real, and it takes a terrible toll.
Sex addicts experience the same story arc as other addicts. They develop the same tolerance to the behavior, whereby more and more sex is necessary to achieve pleasure. They have physical and psychological withdrawal symptoms if they don't engage in it, and repeatedly relapse if they try to quit. And, most tellingly, their liking sex gradually gives way to needing it: What used to be a transcendent pleasure is now simply necessary to face the day.
Of all addiction sufferers, sex addicts are among the least likely to seek help. Our popular culture is highly sexualized, constantly giving us the message that we all deserve the best possible sex all the time. And whether or not they are public figures, sex addicts are unlikely to be treated compassionately, because we tend to believe that others' sexual behavior must be 100 percent volitional.
This is a tragedy. While a conscientious drug addict or alcoholic might be able to inflict pain mostly on himself, sex addicts use other people by definition. As such, they inevitably leave a wide swath of emotional destruction in their wake, severely testing the limits of not just political loyalty, but human compassion.
David J. Linden is a professor of neuroscience at the Johns Hopkins University School of Medicine and the author of "The Compass of Pleasure" (Viking Press, 2011).