Study Finds Link Between Sisters and Rare Postpartum Risk

As maternal mental health emerges as the leading cause of pregnancy-related death in the US, researchers and health systems are finally shifting focus to identify and address mental health risks before they become full-blown emergencies. One of the most dangerous, yet least understood, of these risks is postpartum psychosis—a rare condition that can come on suddenly after birth and escalate quickly, often with devastating consequences if left untreated.

Now, a new study from Mount Sinai is helping to shed light on who may be most at risk, not to scare mothers but rather to prepare them for what’s ahead. The peer-reviewed study—which looked at over 1 million women, of whom 2,514 (0.15%) experienced postpartum psychosis—found that mothers are more than 10 times more likely to develop postpartum psychosis if their full sister has experienced it.

“These findings underscore the exceptional familial and potentially genetic predisposition in cases of postpartum psychosis, even higher than with schizophrenia and bipolar disorder,” Veerle Bergink, MD, PhD, Director of the Women’s Mental Health Center at Mount Sinai said in a statement.

While the relative risk is high among full siblings, the absolute risk—the chance of developing the condition—is still relatively low at 1.6%. But researchers say that doesn’t mean it should be ignored. “Women and their physicians need to be aware of the early signs of the disease so it can be promptly diagnosed and, hopefully, prevented,” emphasizes Bergink.

Postpartum psychosis goes beyond postpartum depression impacting a person’s sense of reality and how they interpret the world around them day-to-day. Early postpartum psychosis symptoms can include severe mood swings, insomnia, hallucinations, disorganized thinking and thoughts of self-harm.

“We should be doing things to ease the burden on these women during the postpartum period, such as ensuring they get more rest or, if they’re bottle-feeding, having their partner take over the nighttime feeding,” Bergink says. “Too many women at higher risk are left on their own with a new baby and no support.”

The good news? Bergink says treatments like lithium and antipsychotic medications can work very well if taken in advance. For moms who’ve had postpartum psychosis before, starting medication right after delivery with future children may help prevent it from happening again. And for women with bipolar disorder or a strong family history of mental health conditions, working with a reproductive psychiatrist during pregnancy can provide a personalized care plan.

The next steps in Mount Sinai’s research are already underway. Behrang Mahjani, PhD, Assistant Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai, is leading research to understand the genes and biological triggers behind postpartum psychosis.

“We’ll be using complex molecular data to investigate the genetic architecture of the disease,” says Dr. Mahjani. “Knowing what specific genes are involved will help us dive into the mechanisms and triggers of postpartum psychosis, and if they’re hormone- or immune-related. And that, in turn, could lead us to novel treatments and ways to proactively inform women of their risk before they’re faced with a severe health crisis.”

This isn’t the first time researchers have identified a powerful sister-to-sister link when it comes to pregnancy outcomes. A study published earlier this year found that sisters of women who experienced pregnancy complications may also face a higher risk of heart disease later in life. The research reinforces a growing understanding that family history, especially among sisters, can offer key clues into a woman’s long-term health during and after pregnancy.