Effect of anxiety on cognition, behavior, and stimulant response in ADHD.

The effect of the comorbidity of overanxious disorder (ANX) in attention deficit hyperactivity disorder (ADHD) on laboratory measures of behavior, cognition, and stimulant response was examined. Seventy-nine children who met DSM-III-R criteria for ADHD were tested further for an oppositional defiant disorder (ODD), conduct disorder (CD), or ANX. Subjects with comorbid ANX showed less impulsiveness on a laboratory measure of behavior and had longer, sluggish reaction times on the Memory Scanning Test than those without ANX. ADHD subjects with comorbid ANX were less frequently diagnosed as CD. Forty-three of the subjects completed a double-blind trial of methylphenidate; subjects with comorbid anxiety had a significantly poorer response to the stimulant than those without anxiety, while the comorbidity of ODD or CD did not affect stimulant response. The results suggest that ADHD with comorbid ANX may represent children with primary anxiety who develop secondary inattentiveness, or they may represent a different subtype of ADHD, perhaps similar to the condition of attention deficit disorder without hyperactivity under DSM-III.