According to a new study co-authored by a professor at Vanderbilt University in Nashville, women’s hormonal cycles may not only make them more prone to drug addiction but also more affected by triggers that lead to relapse.
Assistant professor of pharmacology Erin Calipari and colleagues observed that women represent a particularly large percentage of drug addicts but addiction studies have primary focused on the mechanisms underlying addiction effects in men. Therefore, medication for this vulnerable population has been created with men’s needs in mind, which may be why women often don’t respond well to such medication. Dr. Calipari’s study found that when fertility-related hormone levels are high, women learn faster, make stronger associations to cues in their environment, and are more prone to seek rewards.
In the study, male and female rats were allowed to dose themselves with cocaine by pushing a lever, with a light set up to come on during dosing. That is similar to the environmental cues, such as drug paraphernalia, present when humans are taking drugs. When their circulating hormone levels were high, female rats made stronger associations with the light and were more likely to keep pushing the lever as much as it took to get any amount of cocaine.
Ultimately, females were willing to “pay” more in the presence of these cues to get cocaine. The results are transferable to humans through behavioral economic analysis, which uses a complicated mathematical equation with values for the most and least a subject will do to get a payoff. It’s one of the few ways that comparisons can be made across species.
“There’s epidemiological data that says women are more vulnerable, but it’s unclear what the factors are,” said Dr. Calipari. “We know they transition to addiction faster and have more problems with craving and relapse. Now, with research like this, we’re beginning to isolate environmental and physiological causes.”
Dr. Calipari believes that the next step is figure out specifics of how hormonal shifts affect women’s brains and develop medications that could help override those. In the meantime, she suggests that treatment centers use the information in this study to educate women about their stronger mental connections to places and objects, which may result in a higher chance of relapse.
Dr. Calipari is a graduate of the University of Massachusetts at Amherst, where she earned two bachelor’s degrees in psychology and biology. She holds a Ph.D. in neuroscience from the School of Medicine Wake Forest University in Winton-Salem, North Carolina.
The full study, “Cues Play a Critical Role in Estrous Cycle-Dependent Enhancement of Cocaine Reinforcement,” was published in the journal Neuropsychopharmacology. It may be accessed here.