According to a new study scheduled to appear in the February issue of Journal of Clinical Endocrinology & Metabolism, women who take SSRI antidepressants may experience delayed lactation after giving birth and may need additional support if they chose to breastfeed.

“The breasts are serotonin-regulated glands,” said study co-author Dr. Nelson Horseman of the University of Cincinnati, which means that “the breasts’ ability to secrete milk at the right time is closely related to the body’s production and regulation of the hormone serotonin.” Commonly used antidepressants such as Prozac, Zoloft and Paxil all belong to a class of drugs called SSRIs, which affect serotonin re-uptake, and might also affect serotonin regulation in the breast.

The study looked at the effects of SSRI antidepressants on lactation in the lab by using human and animal cell lines as well as genetically modified mice. In addition, an observational study was carried out which examined 431 mothers who had just given birth.

In the observational study, the median onset of lactation for mothers who had been taking SSRIs was 85.8 hours after childbirth, compared to 69.1 hours in women who had not taken SSRIs. Anything past 72 hours is commonly considered to be delayed lactation by researchers.

“SSRI drugs are very helpful medications for many moms, so understanding and ameliorating difficulties moms experience can help them achieve their goals for breastfeeding their babies,” noted Horseman. “More human research is needed before we can make specific recommendations regarding SSRI use during breastfeeding.”