Perinatal risk factors and subclinical hypomania: A prospective community study.

Background: Perinatal risk factors are implicated in the development of psychopathology, but their role in bipolar disorder (BD) and hypomania is unclear. Using data from a prospective community cohort, this is the first study to investigate the association between a range of perinatal risk factors, hypomanic symptoms, and 'high-risk' for BD in the general population.

Methods: Parent report of perinatal events were available for 26,040 eighteen-month-olds from the Twins Early Development Study. Subsequent self-report hypomania was measured at ages 16 (Hypomania Checklist-16; N = 2943) and 26 (Mood Disorders Questionnaire; N = 7748). Participants were categorised as 'high-risk' for BD using established classifications. Linear and logistic regressions were conducted within a generalised estimating equations framework to account for relatedness in the sample.

Results: Prenatal alcohol exposure (β = 0.08, SE = 0.04, p = .0002) and number of alcohol units consumed (β = 0.09, SE = 0.02, p < .0001) were associated with hypomanic symptoms at age 16, and number of alcohol units (OR = 1.13, 95 % CI:1.06-1.21, p = .0003) and maternal stress (OR = 1.68, 95 % CI:1.21-2.34, p = .002) were associated with 'high-risk' for BD age 16. Prenatal tobacco exposure (β = 0.10, SE = 0.04, p < .0001) and number of cigarettes smoked (β = 0.10, SE = 0.01, p < .0001) were associated with hypomanic symptoms and 'high-risk' for BD at age 26, although these result were attenuated controlling for parental psychiatric history.

Limitations: Familial confounding could not be fully adjusted for. Rater reports include some biases.

Conclusions: These findings show perinatal risk factors to be associated with subclinical hypomania and 'high-risk' for BD. Future work should explore the mechanisms underlying these longitudinal associations, which could shed light on prevention and intervention efforts.