Experiencing a psychiatric episode within the first 30 days post-partum appears to be associated with an increased risk of developing bipolar affective disorder, according to a report published Online First by Archives of General Psychiatry, one of the JAMA/Archives journals.

"Childbirth has an important influence on the onset and course of bipolar affective disorder, and studies have shown that episodes of post-partum psychosis are often best considered as presentations of bipolar affective disorder occurring at a time of dramatic psychological and physiological change," the authors write as background information in the article. "It is also clear, however, that a high number of women with the new onset of a psychiatric disorder in the immediate post-partum period do not receive a diagnosis of bipolar disorder."

Trine Munk-Olsen, Ph.D., of the National Centre for Register-Based Research, Arhus University, Arhus, Denmark, and colleagues collected data on 120,378 women born in Denmark from 1950 to 1991 who were alive in 2006 and had a history of a first-time psychiatric contact with any type of psychiatric disorder (admission or outpatient contact) with any type of psychiatric disorder excluding bipolar affective disorder. Each woman was followed up with individually from the day of discharge, with data collected on inpatient or outpatient psychiatric contacts during the follow-up period.

A total of 2,870 of these women had their initial psychiatric contact within the first year after delivery of their first child. During follow-up, 3,062 of the 120,378 women received diagnoses of bipolar affective disorder, of which 132 had their initial psychiatric contact 0 to 12 months post-partum. After adjusting for first diagnosis and family history of psychiatric illness, conversion rates to bipolar disorder were significantly predicted by the timing of initial psychiatric contact. The authors found a significantly higher conversion rate to bipolar affective disorder in women having their initial contact within the first post-partum month. Additionally, the authors found evidence that the severity of the initial post-partum psychiatric episode may be important, as inpatient admissions were associated with a higher conversion rate than were outpatient contacts.

Fifteen years after initial contact, 13.87 percent of women with onset in the immediate post-partum period (0 to 30 days) had converted to bipolar disorder, 4.69 percent of women with later onset (31 to 365 days post-partum) and 4.04 percent of women with onset at other points had converted to bipolar disorder. Additionally, an extended analysis showed that 18.98 percent of women with onset in the immediate post-partum period had converted to bipolar disorder within 22 years after initial psychiatric contact. Conversely, 6.51 percent of women with later post-partum onset and 5.43 percent of women with onset at other points had converted to bipolar disorder after 22 years.

"The present study confirms the well-established link between childbirth and bipolar affective disorder and specifically adds to this field of research by demonstrating that initial psychiatric contact within the first 30 days post-partum significantly predicted conversion to bipolar affective disorder during the follow-up period," the authors conclude. "Results indicate that the presentation of mental illness in the early post-partum period is a marker of possible underlying bipolarity."