December 3 , 2004

Imaging study finds a structural difference in the brains of cocaine addicts

MGH researchers have identified an unexpected structural difference in the brains of cocaine addicts. In the Nov. 18 issue of Neuron, they describe how a key structure called the amygdala is smaller in cocaine addicts than in healthy volunteers. While the current study cannot determine whether this difference is a cause of addiction or results from drug use, the findings suggest a need to reformulate current strategies for treating cocaine addiction.

Work here and at other centers has identified the amygdala's fundamental role in addiction. "It is important for producing drug craving, which has a powerful effect in maintaining drug abuse," says Hans Breiter, MD, co-director of the Motivation and Emotion Neuroscience Collaboration in the MGH Departments of Radiology and Psychiatry, senior author of the study. "No one anticipated such a specific pattern of volume reduction in the amygdalas of cocaine addicts - pointing to potential problems in a small number of sub-regions of this brain structure."

Earlier studies suggested that cocaine use reduced activity in the amygdala, particularly during times when addicts reported feelings of craving. Using newly developed imaging techniques, the researchers analyzed data gathered in earlier studies of 27 cocaine addicts receiving drug infusions and compared it with information from 27 healthy controls. The amygdalas of cocaine addicts were found to have significantly less volume than those of the healthy controls, reductions that consistently applied to specific areas.

The results are particularly intriguing in light of the amygdala's role in alerting other brain regions to the possibility of undesirable events or bad outcomes. The observed changes could relate to the common difficulty addicts have in evaluating the long-term consequences of their actions. The authors also note that further studies are required to determine definitively whether the amygdala changes precede cocaine addiction or result from drug use.

Gregory Gasic, PhD, and Nikos Makris, MD, are co-first authors of the paper. Other MGH co-authors are Larry Seidman, PhD, Jill Goldstein, PhD, David Gastfriend, MD, Matthew Albaugh, Steven Hodge, David Zeigler, Fred Sheahan, Verne Caviness, MD, PhD, David Kennedy, PhD, and Bruce Rosen, MD, PhD.