Abnormal Affective Responsiveness in Attention-Deficit/Hyperactivity Disorder: Subtype Differences

Background: Emotional-motivational dysfunctions likely contribute to attention-deficit/hyperactivity disorder (ADHD), especially to hyperactive and impulsive symptoms. This study examined the affective modulation of the startle reflex in a large sample of ADHD patients. The aim was to compare subtypes of ADHD. Methods: One hundred ninety-seven unmedicated adult ADHD patients (127 combined type [ADHD-C]; 50 inattentive type (ADHD-I]; 20 hyperactive-impulsive type [ADHD-HI]) and 128 healthy control subjects were examined. The affect-modulated startle response as well as valence and arousal ratings were assessed for pleasant, neutral, and unpleasant picture stimuli. Results: Control subjects exhibited startle response attenuation and potentiation by pleasant and unpleasant pictures, respectively. In ADHD-HI, startle response was not attenuated by pleasant and not potentiated by unpleasant stimuli. In ADHD-C, startle response was not attenuated by pleasant pictures, and ADHD-I responded similar to control subjects but startle response was attenuated to a lesser degree by pleasant stimuli. The ADHD-HI group rated all pictures as more positive, and male ADHD-HI rated unpleasant stimuli as less arousing. Conclusions: This is the first study to assess the affect-modulated startle response in ADHD. It confirms emotional dysfunctions in these patients; all subtypes showed more or less diminished emotional reactions to pleasant stimuli. The hyperactive-impulsive type was also marked by blunted reactions to unpleasant stimuli, Results suggest that response patterns to emotional cues or reward may help to differentiate ADHD subtypes. Blunted emotional reactivity is especially pronounced in ADHD patients with symptoms of hyperactivity and impulsivity (ADHD-C, ADHD-HI).