Abstract
Objective:
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.
Methods:
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.
Results:
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%).
Conclusions:
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.
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