Science  02 Jun 2006:
Vol. 312, Issue 5778, pp. 1287b
DOI: 10.1126/science.312.5778.1287b

Men have higher rates of addiction than do women to most substances. Now researchers may have discovered one reason why: Male brains release up to three times as much dopamine—the “pleasure molecule”—as women do in response to amphetamine use.

Neuroendocrinologist Gary Wand and colleagues at Johns Hopkins University in Baltimore, Maryland, gave 28 men and 15 women doses of amphetamine comparable to what a user might take. Although they found no sex difference in dopamine-receptor density, males showed larger dopamine releases in three of four regions of the striatum, ranging from 50% to 200% greater than the average female release, the team reports in the 15 May issue of Biological Psychiatry. Men also ranked the positive effects of the drug higher than women.

A difference in dopamine release may help explain the sex disparity not only in addictions but in dopamine-related diseases such as Parkinson's, Tourette syndrome, and schizophrenia, which hit males harder than women, says Wand. The findings mirror sex discrepancies in dopamine release observed in mice, says neuroendocrinologist Dean Dluzen of Northeastern Ohio Universities College of Medicine in Rootstown. His studies of Parkinson's disease in mice have revealed greater neurodegeneration in males, and he believes the new study “makes for a strong case” that this is true in humans as well.

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