Perinatal risk factors and subclinical hypomania: A prospective community study

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.

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.

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.

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

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.