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LOS ANGELES — Risk for postpartum psychosis is significantly higher in women who have a sister who has experienced the condition and/or has bipolar disorder (BD), a new study showed.

In a population-based cohort study of nearly 1.7 million women, those with a full sister who had had the disorder were 10 times more likely to have postpartum psychosis than those whose sister did not have it. Odds of developing the condition were doubled when a sister had BD and about 14-fold higher if a sister had both BD and postpartum psychosis.

Although rare, postpartum psychosis is considered “one of the most severe psychiatric conditions,” co-investigator Veerle Bergink, MD, PhD, professor in the Department of Psychiatry, Icahn School of Medicine at Mount Sinai, and director of Mount Sinai’s Women’s Mental Health Center, New York City, and colleagues noted.

If not addressed and treated, the condition has been linked to increased risk for suicide and infanticide. But findings such as these can help clinicians identify those at potentially greater risk and make a plan, Bergink told Medscape Medical News.

“You don’t have to start medication right away, but we do need to be aware” of the risk, she said.

The findings were presented on May 19 at the American Psychiatric Association (APA) 2025 Annual Meeting and were simultaneously published online in the American Journal of Psychiatry.

Relative Risks

Postpartum psychosis typically occurs in the first 3 months after childbirth, with onset most likely in the first month. It can also occur in women who have no history of psychiatric illness and is the leading cause of maternal deaths, the researchers noted.

If a woman shows symptoms of the condition — which include excessive energy, agitation, paranoia, confusion, and sleep problems — it should be addressed as a medical emergency, they added.

Although previous research has shown that genetic factors can contribute to increased postpartum psychosis risk, the magnitude of that contribution has been unclear.

In the current analysis, Bergink and colleagues examined data from Swedish national registers for 1,648,759 women who gave birth between January 1980 and September 2017. The primary outcome was a diagnosis of postpartum psychosis.

Results showed that 2514 of the total participants — only 0.15% — had postpartum psychosis within the first 3 months of the birth of their first child.

However, after adjusting for year and age at childbirth, the relative recurrence risk (RRR) was 10.69 for the condition in mothers with a full sister who had experienced the condition compared with mothers with a sister who had not experienced it (95% CI, 6.6-16.3; P < .001).

Still, the absolute risk for those with an affected sister was estimated at just 1.6%.

In the women diagnosed with postpartum psychosis, 49% had a history of BD, and 24% had a history of other mental health diagnoses. Prevalence of BD was 1.4% for the entire participant population.

The odds ratio (OR) for postpartum psychosis when a sister had BD was 2.1 (95% CI, 1.0-4.0; P = .04). In addition, the combined OR was approximately 14.3 when a sister had experienced postpartum psychosis while also having BD.

The RRR was also increased when a woman had a full woman cousin with postpartum psychosis, but it was not statistically significant when adjusted for birth year and age at childbirth or when adjusted for those factors plus history of BD.

“Our results provide guidance for clinicians working with pregnant women with personal or family histories of postpartum psychosis,” the investigators wrote.

Diagnostic and Statistical Manual of Mental Disorders (DSM) Inclusion?

Bergink noted that the condition is not currently listed as a stand-alone disorder in any version of the DSM. However, numerous research groups are collaborating to develop criteria for its inclusion in future iterations of the manual.

They propose that criteria should include experiencing at least one of the following within 3 months of childbirth, with a duration of at least 1 week or of any duration if hospitalization is necessary: Mania/mixed state, delusions, hallucinations, disorganized speech or thoughts, and disorganized or confused behavior.

Asked during a question-and-answer session if family history screenings are currently being done among women who are pregnant, Bergink answered, “In general, no, but it should be.”

“Because of the potential negative impacts, sometimes severe, on mother and baby, this disorder needs to be identified and effectively treated,” Ned H. Kalin, MD, editor-in-chief of the American Journal of Psychiatry and professor and chair of the Department of Psychiatry at the University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, said in a press release.

The current study is important because it highlighted the increased risk when the condition runs in families, he told Medscape Medical News.

“It also underscores the importance of understanding that risk and of working with your OB-GYN [obstetrician-gynecologist] doctor or psychiatrist to help reduce and mitigate the risk with treatment and close observation,” Kalin said.

Bringing ‘Stigma Out of the Darkness’

Although postpartum psychosis is considered quite rare, tragic aftereffects in some undiagnosed and untreated women have been widely reported in the media.

At the press briefing, Bergink shared that a medical colleague with the condition recently shot and killed herself and her baby girl.

“Unfortunately, not all cases are detected in time. At Sinai, we lost a colleague who had no psychiatric history and her baby,” she said. “That happens. And it can occur in anyone.”

Michael F. Myers, MD, chair of the APA meeting’s Scientific Program Committee, shared that he was involved with two situations where patients had extreme forms of the condition, including one where a woman psychiatrist killed herself and her child.

“You hear about postpartum depression and postpartum blues. But then there’s this subset that is not only dangerous to themselves but also to their baby,” Myers told Medscape Medical News. “Talking about these situations is how we bring the stigma [about the condition] out of the darkness.”

Psychiatric History Not Always a Factor

“There’s a theme that having a psychiatric history is the main predictor for postpartum psychosis. But sometimes we miss it,” Misty C. Richards, MD, associate professor at the University of California, Los Angeles, and medical director of perinatal psychiatry for the university’s Maternal Outpatient Mental Health Services Clinic, said at the briefing.

She added that, as a clinician, “you do the best that you can to try to catch this early because things can become wildly out of control in the postpartum period. Infanticide should just never happen.”

She later told Medscape Medical News that the symptoms of postpartum psychosis differ from those of schizophrenia because they wax and wane and almost present as delirium. 

“So you can be lucid one minute and the next be wildly delusional. It’s usually in the setting of poor sleep and severe anxiety and becomes an emergency very quickly,” Richards said.

She added that this is much more extreme than a normal response to the chaos that often occurs during the first week after delivery.

“People may think, ‘Oh, she’ll shake it off and be okay.’ But no. If you miss it, that’s when it can be catastrophic,” she concluded.

The study was funded by grants from the Beatrice and Samuel A. Seaver Foundation, the National Institute of Mental Health, and the Brain and Behavior Research Foundation, as well as from an Out to Innovate Career Development Fellowship. One investigator reported having served as a consultant for the Motherhood Center of New York, New York City, and another had served as a speaker for Lundbeck. Bergink and the other five investigators, as well as Richards, reported no relevant financial relationships.