Cognitive functioning in ADHD: Inhibition, memory, temporal discounting, decision-making, timing and reaction time variability

Inhibition, memory, temporal discounting, decision-making, timing, and intraindividual variability in reaction time have emerged as key cognitive domains for understanding neurocognitive deficits in individuals with ADHD. In the domain of inhibition, motor inhibition has been studied most extensively, with deficits demonstrated in both restraint and cancellation. Working memory difficulties have been identified using a broad range of tasks. Decision-making has been less well studied, but risky decision-making and temporal discounting have displayed relatively consistent effects. Motor timing, duration discrimination, duration reproduction, and variability on all of these tasks have also been implicated in ADHD. From a clinical perspective, whilst ADHD is clearly associated with a broad range of neuropsychological deficits, there is considerable heterogeneity and none of these deficits is required or necessary for a diagnosis. However, neuropsychological measures may help define cognitive subgroups within ADHD and these may in turn be useful in predicting course, outcome, and treatment response.