Associations between childhood asthma and ADHD: issues of psychiatric comorbidity and familiality.

OBJECTIVE In this paper we evaluate the association between asthma and attention-deficit hyperactivity disorder (ADHD), addressing issues of comorbidity and familiality by formulating and testing competing hypotheses. METHOD Subjects were 6- to 17-year-old boys with DSM-III-R ADHD (N = 140) and normal controls (N = 120) and their first-degree relatives. Information on asthma was obtained from the mothers in a standardized manner blind to the proband's clinical status. RESULTS The risk for asthma did not meaningfully differ between ADHD and control children. Relatives of ADHD probands with and without asthma were at significantly greater risk for ADHD than relatives of normal controls. In contrast, the risk for asthma was significantly elevated only among relatives of children with ADHD plus asthma. CONCLUSIONS These findings argue against a substantial etiological or pathophysiological relationship between the two conditions but suggest that ADHD and asthma are independently transmitted in families. Thus, the observation of ADHD symptoms in an asthmatic child should not be dismissed out of hand as being a consequence of asthma since many asthmatic ADHD children may actually have ADHD.