Mental illness and drug addiction often occur hand-in-hand because they may be linked by neurobiology, a U.S. researcher suggests.

The study, published in Behavioral Neuroscience, found that rats with the amygdala -- the part of the brain linked to fear, anxiety and other emotions -- damaged or found to have lesions at birth grew up showing much less caution than normal plus a heightened response to drugs.

Rats with the abnormal amygdala showed significantly less fear in an elevated maze and kept socializing even when exposed to the scent of a predator.

Lead study author Dr. Andrew Chambers of Indiana University said these same rats also were significantly more sensitive to cocaine after just one exposure.

"Early emotional trauma, paired with a certain genetic background, may alter the early development of neural networks intrinsic to the amygdala, resulting in a cascade of brain effects and functional changes that present in adulthood as a dual-diagnosis disorder," Chambers said in a statement.

Addiction to nicotine, alcohol and drugs often is found in people with a wide variety of mental illnesses, including anxiety disorders, unipolar and bipolar depression and schizophrenia, Chambers said. // Copyright 2007 by United Press International



Publication date: 05 December 2007   

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