Selective enhancement of cost sensitivity by methylphenidate in adult ADHD: a randomized placebo-controlled trial

Attention-deficit hyperactivity disorder (ADHD) is associated with impairments in real-life decisions, many involving balancing costs and benefits. Increasing dopamine and norepinephrine with stimulant medication improves decision-making in ADHD. However, it is unclear whether stimulant medication affects sensitivity to costs and/or benefits or alters the speed-accuracy tradeoff. Here, we applied the drift diffusion model (DDM) to assess how the stimulant medication methylphenidate (MPH) affects subprocesses of cost-benefit decision-making in ADHD.

Sixty-one adult participants with ADHD and 63 healthy controls completed a cost-benefit decision-making task in a randomized double-blind placebo-controlled design. ADHD participants were tested once on and once off MPH. Control participants performed the task in two sessions without medication. The task entailed deciding whether to accept or reject a stimulus based on learned cost and benefit value associations. The effect of ADHD and medication on subprocesses of decision-making was disentangled by estimating task performance with DDM parameters drift rate, starting point bias, and decision threshold, representing evidence accumulation, a priori accept/reject bias, and the speed-accuracy tradeoff, respectively. Primary analyses used a modified intention-to-treat sample, including participants with main-phase data from both sessions.

The DDM analysis identified impaired evidence accumulation combined with premature responding in participants with ADHD, indicated by reduced sensitivity to costs and benefits and narrower decision thresholds. MPH altered the cost-benefit balance by improving sensitivity to costs. Lastly, lower cost sensitivity was associated with greater symptom severity and higher prescribed dosage in ADHD.

Methylphenidate alters cost-benefit decision-making in ADHD by increasing sensitivity to costs.