RATIONALE - Adolescents with attention-deficit/hyperactivity disorder (ADHD) become cigarette smokers at twice the rate of non-ADHD adolescents, and this finding continues into adulthood. Abnormal cognitive/behavioral inhibition is one core cognitive symptom of ADHD, leading to impulsive behavior in people with this disorder. Nicotine, contained in tobacco smoke, is known to improve attention, vigilance, and short-term memory. However, little is known about how nicotine might effect cognitive/behavioral inhibition.
OBJECTIVE - This study tested the hypothesis that acute nicotine administration would improve cognitive/behavioral inhibition in non-smoking adolescents with ADHD.
METHODS - This single-dose, acute, repeated-measures, double blind study in adolescents (13-17 years) with DSM-IV confirmed ADHD assessed the effects of transdermal nicotine, oral methylphenidate, and placebo on inhibition in non-smoking adolescents with ADHD. Dependent measures included tests of cognitive/behavioral inhibition (the stop signal task), cognitive interference control (the Stroop task), and a measure of verbal learning and recognition (the hi-low imagery task).
RESULTS - Results from five subjects indicated that stop signal reaction time (SSRT), an estimate of the speed of inhibiting a response, was significantly (P<0.01) improved following both nicotine and methylphenidate treatment as compared to placebo treatment. Neither "go" reaction time nor accuracy showed any effect of drug. In the Stroop task, another task of cognitive inhibition, nicotine but not methylphenidate significantly (P<0.05) decreased the Stroop effect compared to placebo.
CONCLUSIONS - These results indicate that nicotine administration has measurable positive effects on cognitive/behavioral inhibition in adolescents with ADHD. The size of the effect is at least comparable to methylphenidate. Positive effects of nicotine on inhibitional performance may contribute to higher rates of cigarette use in adolescents with ADHD.