Autoimmune Disorder May Be Linked to Some Cases of Postpartum Psychosis

While postpartum depression is fairly well categorized, postpartum psychosis—a rarer but more severe pregnancy-related illness—is less well studied. About 1 in 1,000 women will develop this disorder, which manifests a few weeks after delivery with both psychotic and mood symptoms.

As with other disorders that have a rapid onset, the causes of these severe psychiatric changes can be difficult to discern, but a new report in AJP in Advance suggests that autoimmune encephalitis may be the culprit about 4 percent of the time.

There has been some speculation that autoimmune problems that trigger encephalitis contribute to a subset of psychiatric disorders. The studies that have screened for encephalitis, however, have revealed that at best it is a very rare contributor to mental disorders, indicating it would not be viable to test for autoimmune encephalitis in patients with the risks posed by false positive results.

“But about 80 percent of the positive cases of encephalitis in these previous screenings were young women, which points to them being a particularly at-risk group,” study co-author Veerle Bergink, M.D., Ph.D., a research psychiatrist at Erasmus Medical Center in Rotterdam, told Psychiatric News. “And pregnancy and [the] postpartum [period] are well-known periods of high immune system activation.”

Bergink and her colleagues screened serum samples from 96 women who developed postpartum psychosis while at the Erasmus Mother-Baby Inpatient Unit and 64 healthy postpartum women.

Four of the patients with postpartum psychosis tested positive for reactive neuronal antibodies, and in two cases (confirmed by two separate assays) the tests specifically identified the antibodies as targeting the NMDA receptor; the target antigen for the other two samples could not be identified. None of the 64 healthy controls tested positive for any neuronal antibodies.

Bergink stated that the four patients shared no other distinct features that could distinguish them from the rest of the postpartum group, though both of the anti-NMDA receptor patients did develop motor problems (extrapyramidal symptoms) following treatment with the antipsychotic haloperidol.

Based on these findings, Bergink suggests that all young women who develop acute postpartum psychosis should be screened for anti-NMDA receptor autoantibodies. Such a screening could be valuable, Bergink says, as around half of the instances of postpartum psychosis actually represent the onset of bipolar disorder, whereas the other half remit after a few months of treatment. (A woman with a prior case of postpartum psychosis has around a 30 percent chance of developing it again following subsequent pregnancies).

“When a woman has a child, it is one of the strongest triggers we know for developing a psychiatric disorder,” Bergink told Psychiatric News. “But does that trigger induce a problem that only manifests during a postpartum period or is it a lifelong vulnerability? That is a huge distinction for the affected women, so we need to understand all the possible causes.”

Bergink said that she and her colleagues plan to continue to track the patient cohort included in this study to see whether any patterns emerge related to the women who go on to develop subsequent bipolar disorder or future acute postpartum psychotic episodes. The researchers are also continuing to screen additional patients and hope that with more samples they may be able to uncover the target antigen for the two women who tested positive for reactive neuronal antibodies, but not for antibodies targeting the NMDA receptor.

According to Bergink, all four women identified with encephalitis recovered fully on standard postpartum psychosis therapy (lithium and/or antipsychotics) and did not require immunotherapy or surgery.

This study was supported in part by funding from the Netherlands Organisation for Scientific Research, Erasmus University. ■