A new Vanderbilt University study has revealed that women’s hormonal cycles may not only make them more prone to drug addiction but also more affected by triggers that lead to relapse.
What makes these findings especially significant is that there are virtually no addiction studies on women that account for these cycles.
Assistant professor of pharmacology at the Vanderbilt Center for Addiction Research, Erin Calipari, points out that women represent a particularly vulnerable population, with higher rates of addiction from drugs, but previous addiction studies have primarily focused on the underlying effects and mechanisms in men.
Her study found that females learn faster, make better associations to cues in their environment and are more prone to seek rewards when fertility-related hormones are high.
“Women becoming addicted to drugs may be a fundamentally different process than men,” Calipari pointed out. “It’s important to understand this because it’s the first step in developing treatments that are actually effective.”
The next step, Calipari said, would be to figure out details on how hormonal shifts affect women’s brains and, eventually, develop medications that could override them. But before those future treatments become available, people could use this information to educate women about their stronger mental connections to places and objects.
For example, just by visiting a place where they used drugs or holding some kind of an object they used in the process, this may trigger a higher chance of relapse.
Historically, researchers have avoided using female animals for medical research specifically so they don’t have to account for influences from hormonal cycles.
Medication development has often focused on correcting male dysfunctions as a result, which could explain why women don’t often respond to available medications or treatments in the same ways as men do, Calipari said.
Her work was recently published in the Neuropsychopharmacology journal in a paper titled “Cues play a critical role in estrous cycle-dependent enhancement of cocaine reinforcement.”
In this study, male and female rats were allowed to ingest cocaine by pushing a lever, with a light set up to come on during dosing. This is similar to the environmental cues present when humans are taking drugs, such as drug paraphernalia.
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 when their circulating hormone levels were high.
Ultimately, female rats were willing to sacrifice more in the presence of these cues to get their cocaine. Through behavioral economic analysis, these results are transferable to humans. The analysis uses a complicated mathematical equation with values for the most and least a subject will do to get a payoff, and it’s one of the few ways that comparisons can be made across species.
“There is epidemiological data that says women are more vulnerable, but it’s unclear what the factors are. 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,” said Calipari.