Methylphenidate increases willingness to perform effort in adults with ADHD

Abstract

BACKGROUND\nA reduced willingness to perform effort based on the magnitude and probability of potential rewards has been associated with diminished dopamine function and may be relevant to attention-deficit/hyperactivity disorder (ADHD). Here, we investigated the influence of ADHD status and methylphenidate on effort-based decisions. We hypothesized that ADHD participants would make fewer high-effort selections than non-ADHD subjects, and that methylphenidate would increase the number of high-effort selections. Furthermore, we hypothesized there would be associations among ADHD severity and methylphenidate-related changes in effort-based and attentional performance across all participants.\n\n\nMETHODS AND PARTICIPANTS\nADHD (n\u202f=\u202f23) and non-ADHD (n\u202f=\u202f23) adults completed the Effort Expenditure for Rewards Task in which participants select between low-effort and high-effort options to receive monetary rewards at varying levels of reward magnitude and probability. A test of attentional performance was also completed.\n\n\nRESULTS\nOverall, participants made more high-effort selections as potential reward magnitude and probability increased. ADHD participants did not make fewer high-effort selections than non-ADHD participants, but ADHD participants showed greater methylphenidate-related increases in high-effort selections. ADHD participants had worse attentional performance than non-ADHD participants. ADHD severity was associated with methylphenidate-related changes in high-effort selections, but not changes in attentional performance.\n\n\nCONCLUSIONS\nThese results indicate that methylphenidate increases the willingness to perform effort in individuals with ADHD, possibly due to disorder-related motivational deficits. This provides support for theories of insufficient effort allocation among individuals with ADHD.\n\n\nTRIAL REGISTRATION\nClinicaltrials.gov Identifier, NCT02630017.