Postpartum women with cocaine addictions may have an easier time achieving lasting abstinence with the help of the naturally occurring hormone progesterone.

A study by professors at the School of Medicine suggests that pregnant women who decide to quit cocaine during pregnancy and take progesterone during and after their pregnancy have an easier time quitting than women who do not. Funded by the U.S. National Institute on Drug Abuse, the study looked at 50 pregnant women across Connecticut with cocaine use disorders. Of the women who abstained from cocaine use during their pregnancies, those who took exogenous progesterone were more likely to maintain abstinence after they gave birth than women who received placebos.

“In our prior work it was striking how committed women were to maintaining abstinence in pregnancy and even after they deliver and then how difficult it was to maintain abstinence,” said Yale professor of psychiatry, epidemiology and obstetrics, gynecology and reproductive sciences Kimberly Ann Yonkers, who was the study’s lead author. “There must be something going on biologically that makes it harder for them [to abstain] after they deliver.”

Pregnant women often abstain from drug use during pregnancy for the sake of their child, Yonkers said. But this abstinence is short-lived — 80 percent of these women relapse a year after they deliver, psychiatry professor and one of the study’s authors Ariadna Forray said. With the help of progesterone, Forray said she sees the possibility for sustaining a woman’s abstinence not just through full term, but long after she has given birth.

In the study, half of the women were given progesterone post-pregnancy, and half were given a placebo. In total, 12 of the 50 women relapsed within a three-month period, but there was a notable pattern in the cases of relapse — of the 12, nine came from the placebo control group and three came from the progesterone treatment group.

Those numbers suggest that progesterone helps postpartum women maintain abstinence, Yonkers said. The study was double blind, meaning both the subjects and the researchers had no knowledge of who was receiving a placebo and who was receiving progesterone. Cocaine use was measured by a weekly positive urine test and daily self-reports from the women. The urine test data were not statistically significant, Yonkers said, because there were not enough data points. The researchers tried to begin progesterone treatment as soon after delivery as possible, with some women receiving the hormone just a few days after they gave birth, said Cristine Hine, a social worker at the School of Medicine who co-authored the study.

Most of the women were recruited during their first trimester of pregnancy and onward, Hine said. The scientific literature on preclinical animal trials suggests that progesterone has an anti-craving effect, Yonkers said, adding that her research is the first of its kind because few studies have been done on human patients. Nonsynthetic progesterone, a hormone produced in women and one of two main hormones involved in pregnancy and menstruation, is a substance that primary care doctors and obstetricians can prescribe, making it a drug readily available to most women, Forray said.

Although the study’s central recruitment center was Yale-New Haven Hospital, women came from towns as far away as Waterbury, Danbury and Bridgeport. Forray attributed the success of the study to strong engagement between the researchers and the patients, something which she said many similar studies lack.

“Women who abuse substances in pregnancy often don’t get treated very nicely because people see them as substance users and not as pregnant women,” Forray said, adding that cocaine users are a challenging population to work with, as they often fail to follow up with the research. She said the women in this study were noticeably committed to the mission of the research.

Although this study is unique in subject and method, other research on cocaine addiction and progesterone has been done. A 2007 study by Yale psychiatry professor and one of this study’s authors Mehmet Sofuoglu examined the effect of progesterone on male cocaine users. But the study showed no effect of progesterone on reducing cocaine use in men. Forray cited a study done by Columbia psychiatry professor Suzette Evans that examined progesterone treatments among nonpregnant women with CUDs. The uniqueness of the Yale research is the way it recruited women during pregnancy and followed them throughout pregnancy and after they gave birth, she said.

Forray is currently conducting a similar study to Yonkers’, this time with postpartum tobacco users. More women smoke during pregnancy than use cocaine, Forray said, and she hopes to prevent postpartum relapse among female smokers and former smokers by using progesterone.

“I think that this should be replicated in a larger sample size of postpartum women who attained abstinence,” said Yonkers.

The U.S. National Institute on Drug Abuse was incorporated into the National Institutes of Health in 1992.