In the days after giving birth, about one in 1,000 mothers faces a psychiatric emergency so severe it can include hallucinations, delusions, and dangerous impulses—yet for decades, postpartum psychosis has remained largely invisible in genetic research. Now, scientists at the Icahn School of Medicine at Mount Sinai have uncovered the biological truth at its core: the condition has a substantial genetic basis, with about 55% of risk attributable to inherited factors, opening a new pathway toward understanding, predicting, and treating what many have long dismissed as mere weakness or parenting failure.
The landmark study, led by Behrang Mahjani, Ph.D., and published in Molecular Psychiatry, combined whole genome sequencing with Swedish national health registry data and genetic information from the National Institutes of Health's All of Us Research Program—an unprecedented scale for studying one of psychiatry's rarest conditions. The research identified rare damaging mutations in the gene HMGCR, which encodes an enzyme central to cholesterol production, as associated with increased postpartum psychosis risk. This finding surprised even the researchers themselves, but the biology proved coherent: cholesterol is a precursor for steroid hormone synthesis, and the postpartum period triggers dramatic hormonal and metabolic shifts that reshape the body's chemistry.
Beyond the cholesterol connection, the team discovered something equally striking—significant genetic overlap between postpartum psychosis and autoimmune diseases including rheumatoid arthritis, Sjögren's syndrome, myasthenia gravis, and Crohn's disease. This aligns with long-standing clinical observations that autoimmune activity often changes in the postpartum period, suggesting immune biology plays a previously unrecognized role in the illness. The researchers also confirmed genetic links to bipolar disorder and schizophrenia, situating postpartum psychosis within a broader landscape of psychiatric and immune-related conditions.
The stakes of understanding this condition are profound. Postpartum psychosis carries elevated risks of suicide and infanticide, making it a true medical emergency. Symptoms—delusions, hallucinations, severe mood swings, confusion, and disorganized behavior—can emerge within days of birth, leaving mothers and their families in crisis. Yet historically, the condition has been understudied at the genetic level, and stigma has often obscured its biological nature. Mahjani's team is determined to change this narrative. "Postpartum psychosis is a biological illness with a substantial genetic basis," he explained. "It is not a parenting failure or a personal weakness, and women affected by it deserve the same medical seriousness afforded to other severe illnesses."
The heritability estimates—55% from family data and approximately 46% from common genetic variants—underscore how much of the condition's risk is written into our DNA. Yet this is only the beginning. Veerle Bergink, MD, Ph.D., Director of the Women's Mental Health Research Center at Mount Sinai, cautioned that multiple genes are involved and that HMGCR serves as a research tool for further discovery rather than a single answer. The team's next steps include expanding sample sizes and improving ancestral diversity in their research, recognizing that past genetic studies have often underrepresented non-European populations.
For women at risk and their families, these findings promise a future where postpartum psychosis is recognized not as a character flaw but as a medical condition rooted in biology—one that can be anticipated, prevented, and treated with the urgency and care it demands.