Postpartum psychosis most likely in month after childbirth

Mothers with no previous history of mental illness face the greatest risk for postpartum psychosis during the first month after childbirth, a new study suggests.

Postpartum depression is a common problem for many women in the days following delivery. But about one in 1,000 new mothers develops postpartum psychosis, a serious mental illness involving delusional thoughts, hallucinations and the inability to distinguish between reality and imagination.

The new study found that first-time mothers who suffer postpartum psychosis faced the highest risk in the first month after delivery, and that the problem can strike women who had no previous history of mental illness.

In the study, published online February 9 in PLoS Medicine, epidemiologist Unnur Valdimarsdóttir of the Karolinska Institute in Stockholm and colleagues used hospital records to track first-time mothers during the 90 days following childbirth. Of the almost 750,000 women in the study, 892 developed postpartum psychosis, with most cases reported within a month of childbirth. The rapid reduction in hormone levels after childbirth could trigger the psychosis in some women, the authors suggest.

Earlier studies show that schizophrenic women face the greatest risk of psychosis when hormone levels are low. Trauma associated with the pregnancy and birth itself could also contribute to postpartum psychosis, Valdimarsdóttir says.

The study found that about half of the women who developed postpartum psychosis had no previous history of hospitalization for mental illness. “Postpartum psychosis could be the only psychotic episode a woman ever experiences,” says Valdimarsdóttir. “But for a significant number of women, childbirth can set off a recurring psychotic disorder.”

Genetics can also play a role. “Perhaps the hormonal fluctuations trigger psychosis in women who already have a genetic predisposition for developing mental illness,” comments Donna Stewart, a psychiatrist at the University of Toronto. “Even women who had never been hospitalized for mental illness could have received outpatient care, or had a family history of psychiatric problems.”
The researchers found that the risk of developing psychosis increased for mothers over the age of 35. “This could be because older first-time mothers are more likely to have a problematic pregnancy,” Valdimarsdóttir says. Other factors, such as higher infant birth weight and maternal diabetes, lessened the risk. Mothers with diabetes tend to have larger babies, says Valdimardóttir, but why maternal diabetes would lessen the risk of postpartum psychosis is not known. “Perhaps it’s because these mothers are more closely monitored throughout their pregnancy,” Valdimarsdóttir suggests.