Marc Potenza, a psychiatrist at Yale and the director of the school’s Program for Research on Impulsivity and Impulse Control Disorders, has been treating addiction for more than two decades. Early in his career, he, like most others studying addiction at the time, focussed on substance-abuse problems—cocaine and heroin addicts, alcoholics, and the like. Soon, however, he noticed patients with other problems that were more difficult to classify. There were, for example, the sufferers of trichotillomania, the inescapable urge to pull your hair until it falls out. Others had been committed for problem gambling: they couldn’t stop no matter how much debt they had accumulated. It was to this second class of behaviors—at the time, they were not called addictions—that he turned his attention. Were they, he wondered, fundamentally the same?
In some sense, they aren’t. A substance affects a person physically in a way that a behavior simply cannot: no matter how severe your trichotillomania, you’re not introducing something new to your bloodstream.