Hosang GM, et al. - Via a twin study of 13,532 Swedish twin pairs aged 9 and 12 years at recruitment, researchers investigated the degree to which genetic and environmental risk factors for attention-deficit/hyperactivity disorder (ADHD) traits, across childhood and adolescence, were related to adolescent hypomanic symptoms. Particularly for the hyperactivity-impulsivity ADHD symptom domain vs the inattention domain, ADHD and hypomanic symptoms were significantly related. Between 13% and 29% of the genetic risk factors for hypomania were also correlated with ADHD, with greater estimates disocvered for symptoms of hyperactivity-impulsivity in comparison with inattention. Genetic factors distinct to adolescent hypomania were related to 25% to 42% of its variations, inferring some etiologic difference between these forms of psychopathology. In childhood and adolescence, more than a quarter of the genetic risk factors for adolescent hypomanic traits were also correlated with ADHD symptoms, with hypomania-specific genetic risk factors discovered. ADHD and hypomanic symptoms were related to shared genetic factors, which should be the focus of additional study.