While studying the ways cocaine constricts the blood vessels in the brain, Harvard pharmacologist Marc Kaufman noticed that female addicts generally did better in rehabilitation therapy and suffered less neural damage than did males with comparable habits. The reason, he believes, is that the women may be benefiting from hormonal changes associated with their menstrual cycle.
Kaufman took MRI brain scans of men and of a group of women at different phases of their menstrual cycle, after giving them the equivalent of two lines of cocaine. Men suffered a 20 percent drop in brain blood flow, while women at the beginning of their cycle showed no change. Even women in later menstrual stages had only a 10 percent decline. Kaufman believes estrogen's ability to relax blood vessels may lead to a hormone therapy for both male and female cocaine users.