A new imaging study reveals that the brains of cocaine addicts are altered compared to those of nondrug users. Specifically, the volume of the amygdala, a brain region associated with the ability to judge consequences, is significantly smaller in heavy drug users.

Previous research revealed that the amygdala exhibits reduced activity in drug addicts during periods of cravings. In the new work, Hans C. Breiter of Massachusetts General Hospital (MGH) and his colleagues used magnetic resonance imaging (MRI) to study the brains of 27 cocaine addicts and a matched group of nonaddicts. They determined that the almond-shaped amygdala was between 13 and 23 percent smaller by volume in addicts than it was in the control subjects. In combination with other work this study suggests that, when the opportunity for excitement presents itself, some people cannot make good judgements--just like teenagers who take excessive risks in pursuit of thrills, says study co-author David R. Gastfriend, also at MGH. It looks like this is a continuing problem for people with cocaine addiction, and now we know where in the brain that problem resides.

It remains unclear whether cocaine use induces changes to the brain's structure or if a smaller amygdala might make a person more susceptible to cocaine addiction. The researchers note that long-term studies of addicts, as well as family-based studies, could help clarify whether this brain feature is a cause or an effect. No matter if these changes reflect a predisposition to addiction or very rapid degenerative changes, there are clear public policy implications, Breiter remarks. Further research will help us better understand the implications of these changes and develop ways to apply them to preventing or treating cocaine addiction.