%0 Journal Article %T Comparative familial aggregation of bipolar disorder in patients with bipolar I and bipolar II disorders %A Gordon B Parker %A Mia Romano %A Rebecca K Graham %A Tahlia Ricciardi %J Australasian Psychiatry %@ 1440-1665 %D 2018 %R 10.1177/1039856218772249 %X We sought to quantify the prevalence and differential prevalence of a bipolar disorder among family members of patients with a bipolar I or II disorder. The sample comprised 1165 bipolar and 1041 unipolar patients, with the former then sub-typed as having either a bipolar I or II condition. Family history data was obtained via an online self-report tool. Prevalence of a family member having a bipolar disorder (of either sub-type) was distinctive (36.8%). Patients with a bipolar I disorder reported a slightly higher family history (41.2%) compared to patients with a bipolar II disorder (36.3%), and with both significantly higher than the rate of bipolar disorder in family members of unipolar depressed patients (18.5%). Findings support the view that bipolar disorder is heritable. The comparable rates in the two bipolar sub-types support the positioning of bipolar II disorder as a valid condition with strong genetic underpinnings %K bipolar disorder %K heritability %K family history %U https://journals.sagepub.com/doi/full/10.1177/1039856218772249