Evidence of familial association between attention deficit disorder and major affective disorders.

With the use of family study methods and assessments by "blinded" raters, we tested hypotheses about patterns of familial association between DSM-III attention deficit disorder (ADD) and affective disorders (AFFs) among first-degree relatives of clinically referred children and adolescents with ADD (73 probands, 264 relatives) and normal controls (26 probands, 92 relatives). Among the 73 ADD probands, 24 (33%) met criteria for AFFs (major depression, n = 15 [21%]; bipolar disorder, n = 8 [11%]; and dysthymia, n = 1 [1%]). After stratification of the ADD sample into those with AFFs (ADD + AFF) and those without AFF (ADD), familial risk analyses revealed the following: (1) the relatives of each ADD proband subgroup were at significantly greater risk for ADD than were relatives of normal controls; (2) the age-corrected morbidity risk for ADD was not significantly different between relatives of ADD and ADD + AFF (27% vs 22%); however, these two risks were significantly greater than the risk to relatives of normal controls (5%); (3) the risk for any AFF (bipolar disorder, major depressive disorder, or dysthymia) was not significantly different between relatives of ADD probands and ADD + AFF probands (28% and 25%), but these two risks were significantly greater than the risk to relatives of normal controls (4%); (4) ADD and AFFs did not cosegregate within families; and (5) there was no evidence for nonrandom mating. These findings are consistent with the hypothesis that ADD and AFFs may share common familial vulnerabilities.