It is estimated that 1 out of 10 women in the United States (U.S.) take antidepressants, many of them while pregnant or breastfeeding. According to the Centers for Disease Control and Prevention (CDC), between 1995 and 2002 the use of antidepressants rose 48 percent. Antidepressants are among the most prescribed drugs in the U.S. For many this is good news, suggesting that women suffering with depression or postpartum depression are finally seeking help. Others are less enthusiastic, citing the increased use of antidepressants among children and adolescents, despite a lack of evidence to show that they are effective or safe.

What are SSRIs?
Selective serotonin reuptake inhibitors (SSRIs) are among the most common antidepressants. The first drug in this class, fluoxetine, commonly known as Prozac, was released in 1987 followed by Paxil, Zoloft, and others. SSRIs are designed to boost serotonin levels. Serotonin is a hormone produced in the brain that helps transmit signals from one part of the brain to another. Serotonin can affect a wide range of body functions including mood, memory, appetite, temperature, sleep, and social behavior. It is widely believed that serotonin plays a role in depression. People suffering from depression typically have low levels of serotonin. It’s unclear whether low levels of serotonin cause depression or if depression brings about low serotonin levels. Recent data suggest that serotonin may also play a role in milk production.

Do SSRIs affect milk production?
In a study in the Journal of Endocrinology and Metabolism, Aaron Marshall, Laurie Nommsen-Rivers and colleagues at the University of Cincinnati and the University of California at Davis examined the effects of SSRI drugs on lactation using laboratory studies of human and animal cell lines and lactating mice.

Because the breasts’ ability to secrete milk is related to the body’s production and regulation of serotonin, the researchers hypothesized that women taking an SSRI drug might experience a delay in the onset of abundant milk production (a phenomenon referred to as lactogenesis) that typically occurs in the early days after birth.

“I was able to examine this hypothesis using data from an observational study of 431 breastfeeding, first-time mothers. Only eight of the women were taking an SSRI medication, but it is notable that seven of the eight did experience delayed onset of lactogenesis (defined as occurring after 72 hours postpartum) and the eighth woman experienced onset right at 72 hours. Median onset of lactation was 85.8 hours postpartum for the SSRI-treated mothers and 69.1 hours for mothers not treated with SSRI drugs,” said Nommsen-Rivers.

“Perhaps the most alarming finding is the timing of lactogenesis for the entire sample of women (69.1 hours),” said Nommsen-Rivers. “Evidence is mounting that the timing of lactogenesis is occurring much later in mothers here in the U.S. as compared to other countries, and this broader issue deserves our attention.”

Is it safe?
The effect of SSRIs on breastfeeding babies depends on a number of factors such as the gestational and chronological age of the baby, the health of the baby, the dose of the drug, and the drug’s characteristics (bioavailability, molecular weight, half-life etc.) According to Thomas Hale, PhD., author of Medications and Mothers’ Milk, available data suggest that Zoloft (sertraline) and Paxil (paroxetine) are far less likely to transfer into mothers’ milk and therefore babies compared to Prozac (fluoxetine). If women taking Prozac are unable to switch to another SSRI, given the many benefits of breastfeeding, Dr. Hale suggests that these women still be encouraged to breastfeed, mindful to watch their babies for possible side effects such as irritability, excessive crying, colic, and seizures.

Given the small number of SSRI users in the study, these results must be interpreted cautiously. Even though seven of the eight women experienced a delay in the onset of abundant milk production, all went on to breastfeed successfully. More human studies are needed before any type of clinical recommendation can be made regarding the use of SSRI medications. In the meantime, women taking SSRIs should be encouraged to breastfeed, but should be made aware that the onset of abundant milk production may be delayed. Also, health care providers should be prepared to provide additional support if needed.

Women who are pregnant or breastfeeding should check with their doctor or their baby’s doctor before taking any medication, including drugs available over-the-counter. As with all medications, consideration must be given to the benefits and the risks. Although there may be risks associated with taking SSRIs while breastfeeding, untreated depression can be far more dangerous for mothers and babies.