Familiality of Psychiatric Disorders and Risk of Postpartum Psychiatric Episodes: A Population-Based Cohort Study.

OBJECTIVE: Postpartum psychiatric disorders are common and morbid complications of pregnancy. The authors sought to evaluate how family history of psychiatric disorders is associated with postpartum psychiatric disorders in proband mothers with and without a prior psychiatric history by assessing degree of relationship, type of disorder, and sex of family members. METHOD: The authors linked Danish birth and psychiatric treatment registers to evaluate familial risk of postpartum psychiatric episodes in a national population-based cohort. Probands were first-time mothers who were born in Denmark in 1970 or later and who gave birth after age 15 and before Dec. 31, 2012 (N=362,462). The primary exposure was a diagnosed psychiatric disorder in a relative. Cox regression models were used to estimate the hazard ratio of postpartum psychiatric disorders in proband mothers. RESULTS: The relative risk of psychiatric disorders in the postpartum period was elevated when first-degree family members had a psychiatric disorder (hazard ratio=1.45, 95% CI=1.28-1.65) and highest when proband mothers had a first-degree family member with bipolar disorder (hazard ratio=2.86, 95% CI=1.88-4.35). Associations were stronger among proband mothers with no previous psychiatric history. There were no notable differences by sex of the family member. CONCLUSIONS: Family history of psychiatric disorders, especially bipolar disorder, is an important risk factor for postpartum psychiatric disorders. To assist in identification of women at risk for postpartum psychiatric disorders, questions related to female and male first-degree relatives with bipolar disorder are of the highest importance and should be added to routine clinical screening guidelines to improve prediction of risk.