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News from the Johns Hopkins Department of Psychiatry and Behavioral Sciences
Counselors in substance abuse clinics have long thought more men than women are dependent on amphetamines. Epidemiological studies back up those suspicions. Also, men are also more likely than women to suffer toxic effects from what’s known on the street as “speed.”
Now Hopkins research just out in The Journal of Biological Psychiatry, suggests a reason why: When exposed to the drug, men apparently release more dopamine, the neurotransmitter associated with stimulating reward centers in the brain’s ventral striatum. Using PET imaging, Psychiatry’s Cynthia Munro, Ph.D., Mary McCaul, Ph.D., and Dean Wong, M.D., Ph.D., with other Hopkins colleagues, showed that, in the healthy adults studied—most were in their 20s—men released roughly 50 percent more of the neurotransmitter. They also reported more positive feelings from the amphetamine—more pleasure and fewer negative effects like anxiety or dizziness—than did the women.
“This is the first study in people to tie actual brain differences to the gender effect we’ve been observing,” says Munro. “We suspect that the fact that men appear to enjoy methamphetamine more makes them especially susceptible.” The researchers also say the principle may apply to other addictions, such as alcohol, though, of course, that’s open to study.
Most intriguing, they add, is that other diseases with psychiatric symptoms, such as Parkinson’s disease, Huntington’s disease, Tourette syndrome and obsessive compulsive disorder not only show strong gender differences but also affect dopamine-releasing systems in the brain.