Objective: First-degree relatives of persons with mood disorder who attempt suicide are at greater risk for mood disorders and attempted or completed suicide. This study examined the shared and distinctive factors associated with familial mood disorders and familial suicidal behavior.
Method: First-degree relatives' history of DSM-IV-defined mood disorder and suicidal behavior was recorded for 457 mood disorder probands, of whom 81% were inpatients and 62% were female. Probands' lifetime severity of aggression and impulsivity were rated, and probands' reports of childhood physical or sexual abuse, suicide attempts, and age at onset of mood disorder were recorded. Univariate and multivariate analyses were carried out to identify predictors of suicidal acts in first-degree relatives.
Results: A total of 23.2% of the probands with mood disorder who had attempted suicide had a first-degree relative with a history of suicidal behavior, compared with 13.2% of the probands with mood disorder who had not attempted suicide (odds ratio=1.99, 95% CI=1.21-3.26). Thirty percent (30.8%) of the first-degree relatives with a diagnosis of mood disorder also manifested suicidal behavior, compared with 6.6% of the first-degree relatives with no mood disorder diagnosis (odds ratio=6.25, 95% CI=3.44-11.35). Probands with and without a history of suicide attempts did not differ in the incidence of mood disorder in first-degree relatives (50.6% versus 48.1%). Rates of reported childhood abuse and severity of lifetime aggression were higher in probands with a family history of suicidal behavior. Earlier age at onset of mood disorder in probands was associated with greater lifetime severity of aggression and higher rates of reported childhood abuse, mood disorder in first-degree relatives, and suicidal behavior in first-degree relatives.
Conclusions: Risk for suicidal behavior in families of probands with mood disorders appears related to early onset of mood disorders, aggressive/impulsive traits, and reported childhood abuse in probands. Studies of such clinical features in at-risk relatives are under way to determine the relative transmission of these clinical features.