Sibling Psychiatric Disorders as Risk Markers for Postpartum Psychosis
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Background
Postpartum psychosis affects 1–2 per 1,000 women following childbirth and constitutes a psychiatric emergency with significant risks for maternal and infant outcomes. While a personal history of bipolar disorder is the most established risk factor, nearly half of affected women have no prior psychiatric diagnosis, underscoring the need for improved risk stratification strategies.
Methods
In this nationwide Swedish register-based cohort study, we analyzed 676,293 women with at least one sister who delivered their first liveborn child between 1980 and 2017. A secondary analysis included 100,652 women with at least one brother. Postpartum psychosis was defined as psychiatric hospitalization for mania, psychosis, or depression with psychotic features within 90 days postpartum. Associations between sibling psychiatric diagnoses and postpartum psychosis were estimated using logistic regression, adjusting for maternal age and birth year. Hierarchical clustering was applied to identify familial subtypes based on sibling psychiatric profiles.
Results
Among 885 women (3.7 per 1,000) diagnosed with postpartum psychosis, we observed strong associations with sister diagnoses of schizoaffective disorder (OR, 14.50; 95% CI, 4.44– 34.30) and postpartum psychosis (OR, 10.69; 95% CI, 6.60–16.26). Significant associations were also found for sister diagnoses of schizophrenia (OR, 7.10; 95% CI, 1.76–18.60) and bipolar disorder (OR, 6.26; 95% CI, 4.00–9.29). In brother-sister pairs, the strongest association was with bipolar disorder (OR, 6.23; 95% CI, 2.21-13.67). Cluster analysis revealed four familial subtypes, with 6.3% of cases showing distinct patterns of familial psychiatric burden: predominantly internalizing (anxiety/bipolar/personality disorders), predominantly externalizing (substance use disorders), and a broad affective-psychotic pattern with multiple comorbidities.
Conclusions
Familial psychiatric disorders, particularly those with psychotic or affective features, are strong risk markers for postpartum psychosis. These findings support the conceptualization of postpartum psychosis as a disorder with heterogeneous familial liability and highlight the potential utility of incorporating sibling psychiatric history into perinatal mental health screening, especially for women without prior psychiatric diagnoses.
