Genetic risk for bipolar disorder and psychopathology from childhood to early adulthood

Studying the phenotypic manifestations of increased genetic liability for Bipolar Disorder (BD) can increase understanding of this disorder.

We assessed whether genetic risk for BD was associated with childhood psychopathology and features of hypomania in young adulthood within a large population-based birth cohort.

We used data from the second Psychiatric Genetics Consortium Genome Wide Association Study (GWAS) for Bipolar Disorder to construct a polygenic risk score (PRS) for each individual in the Avon Longitudinal Study of Parents and Children (ALSPAC). Linear and logistic regression models were used to assess associations between the BD-PRS and emotional/behavioural difficulties, attention deficit hyperactivity disorder (ADHD) and borderline personality disorder (BPD) traits in childhood, as well as hypomania in early adulthood (sample sizes from 2654 to 6111).

The BD-PRS was not associated with total hypomania score, but was weakly associated with a binary measure of hypomania (OR = 1.13, 95%CI 0.98,1.32; p = 0.097), and particularly at higher hypomania symptom thresholds (strongest evidence OR = 1.33, 95%CI 1.07, 1.65; p = 0.01). The BD-PRS was also associated with ADHD (OR = 1.31, 95%CI 1.10, 1.57; p = 0.018), but not with other childhood psychopathology.

The PRS only captures common genetic variation and currently explains a relatively small proportion of the variance for BD.

The BD-PRS was associated with ADHD in childhood, and weakly with adult hypomania, but not with other psychopathology examined. Our findings suggest that genetic risk for BD does not appear to manifest in childhood to the same extent as schizophrenia genetic risk has been reported to do.