Stimulant Treatment Trajectories Are Associated With Neural Reward Processing in Attention-Deficit/Hyperactivity Disorder

Objective: The past decades have seen a surge in stimulant prescriptions for the treatment of attention-deficit/hyperactivity disorder (ADHD). Stimulants acutely alleviate symptoms and cognitive deficits associated with ADHD by modulating striatal dopamine neurotransmission and induce therapeutic changes in brain activation patterns. Long-term functional changes after treatment are unknown, as long-term studies are scarce and have focused on brain structure. In this observational study (2009-2012), we investigated associations between lifetime stimulant treatment history and neural activity during reward processing.Methods: Participants fulfilling DSM-5 criteria for ADHD (N = 269) were classified according to stimulant treatment trajectory. Of those, 124 performed a monetary incentive delay task during magnetic resonance imaging, all in their nonmedicated state (n(EARLY& INTENSE) = 51; n(LATE& MODERATE) = 49; n(EARLY& MODERATE) = 9; n(NAIVE) = 15; mean age = 17.4 years; range, 10-26 years). Whole-brain analyses were performed with additional focus on the striatum, concentrating on the 2 largest treatment groups.Results: Compared to the late-and-moderate treatment group, the early-and-intense treatment group showed more activation in the supplementary motor area and dorsal anterior cingulate cortex (SMA/dACC) during reward outcome (cluster size = 8,696 mm(3); P-CLUSTERConclusions: Our findings are compatible with previous reports of acute increases of SMA/dACC activity in individuals with ADHD after stimulant administration. Higher SMA/dACC activity may indicate that patients with a history of intensive stimulant treatment, but currently off medication, recruit brain regions for cognitive control and/or decisionmaking upon being rewarded. No striatal or structural changes were found.