Findings demonstrate that subsyndromal hypomania’s etiology overlaps with bipolar disorder (BD), major depressive disorder, and schizophrenia, suggesting that it could represent a continuous trait for psychiatric disorders reflected at its extreme.

• Researchers investigated the specific and shared genetic and environmental architecture of subsyndromal hypomania and BD, schizophrenia, and major depressive disorder in young adults.

• They analyzed a total of 8,568 twin pairs aged 18 years (9,381 [54.7%] female).

• They found higher heritability estimates for hypomania for male individuals vs female individuals (59% vs 29%).

• Moderate genetic and nonshared environmental correlations were found between hypomania and BD.

• Hypomania was found to be significantly linked with the polygenic risk scores for schizophrenia and major depressive disorder but not for BD.