Stimulants, cognition and ADHD

- Effects on cognition are small to moderate both in patients and healthy individuals.
- There is paucity of long-term studies on cognitive effects of stimulants.
- Stimulants are associated with favorable outcomes in epidemiological studies.
- Effects on emotions and motivation should be systematically investigated.
- Harmonization of constructs and tasks is needed.

Psychostimulants such as methylphenidate and amphetamine are the first-line pharmacologic treatments for Attention-Deficit/Hyperactivity Disorder (ADHD). They are considered prototypical cognitive enhancers but their effects on standard laboratory indices of cognitive function are modest when administered acutely, and even less substantial chronically. However, large-scale observational studies in patients with ADHD have detected stimulant-associated decreases of criminal acts, transportation accidents, slightly improved academic performance, and possible protection against drug abuse. These effects likely reflect modulation of broader domains such as emotional regulation and motivation which have been under-examined. Efforts to clarify the ontological relations between cognitive tasks and their underlying constructs should be incorporated into the Research Domain Criteria project and similar harmonization initiatives.