Principal investigator Dr. Hans Breiter of the Massachusetts General Hospital says some of the abnormalities may reflect an inborn vulnerability to drug use, while others appear to be the result of long-term cocaine exposure.

"These data point to a mixture of both drug effects and predisposition underlying the structural alterations we observed," Breiter says in a statement. "They also suggest that a key feature of addiction -- reduction in the range of activities in which addicts participate -- has a neural signature in the form of reduced cortical -- the outer portion of an organ -- thickness in frontal regions of the brain."

In comparison to their healthy counterparts, cocaine addicts were found to have significantly less overall cortical volume, particularly in areas regulating reward function and involved with decision-making. The marked cortical thinness of areas involved in reward regulation and attention was not compensated by increases in other areas, the study says.

The study appears in the journal Neuron.