Stopping and changing in adults with ADHD.
BACKGROUND
A lack of inhibitory control has been suggested to be the core deficit in children with attention deficit hyperactivity disorder (ADHD). This means that a primary deficit in behavioral inhibition mediates a cascade of secondary deficits in other executive functions, such as arousal regulation. Clinical observations have revealed that with increasing age symptoms of hyperactivity and impulsivity decline at a higher rate than those of inattention. This might imply that a deficit in attention rather than a lack of inhibitory control is the major feature in adult ADHD.


METHODS
To study whether an attentional or inhibitory deficit predominates, the stop-signal task and the stop-change task were presented to 24 adults with ADHD combined subtype and 24 controls.


RESULTS
Relative to controls, the stop-signal reaction time (SSRT) was significantly more prolonged than the go-stimulus reaction time (RT) in patients with ADHD. This disproportionate elongation of the SSRT was comparable across tasks, even though the stop-change task exerted more complex (or at least different) demands on the inhibitory system than the stop-signal task. ADHD patients had a higher proportion of choice errors, possibly reflecting more premature responses. Specifically in the stop-change task, patients had more variable choice responses and made more inappropriate change responses, which may also reflect enhanced impulsivity.


CONCLUSIONS
The results support a core deficit in behavioral inhibition in adults with ADHD. We further suggest that there is more evidence for a critical role of deficient inhibitory control in adults than in children with ADHD.
Department of Psychopharmacology, Utrecht University, The Netherlands. E.M.Bekker@pharm.uu.nl
E M
EM
Bekker
C C
CC
Overtoom
J L
JL
Kenemans
J J
JJ
Kooij
I
I
De Noord
J K
JK
Buitelaar
M N
MN
Verbaten
D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000175:diagnosis / Q000523:psychology*; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D012720:Severity of Illness Index