Family studies determine whether affective disorders aggregate within families.  Controlled family studies of patients with bipolar disorder have consistently shown a significantly higher relative risk of bipolar disorder (approximately 4-17%) among th relatives of both people with major depressive disorder and bipolar patients compared to the relative risk among the relatives of healthy controls. (Millon, Blaney, & Davis, 1999)

The risk for developing bipolar disorder is seven times higher in families with a history of the disorder than in the general population.

This table shows the results of some family studies that were conducted in the past (1966-1987) and it shows that there is a greater lifetime prevalence of bipolar disorders found among the first degree relatives of patients with bipolar disorders (6.1%), but a prevalence of bipolar disorder is not found to any significant degree in the relatives of those with unipolar disorders.  However, unipolar disorders are found among the relatives of patients with bipolar. (Zuckerman, 1999)

**To see a presentation of a family study by William McInnis go here --->  Family Study **