A META-ANALYSIS OF PRESCRIPTION STIMULANT EFFICACY: ARE STIMULANTS NEUROCOGNITIVE ENHANCERS?

Abstract

Prescription stimulant use for neurocognitive enhancement is a significant problem among college students with and without ADHD. The primary reason students report misusing stimulant medication is to enhance academic functioning. Given that increasing numbers of students are misusing prescription stimulants, it is critical to explore whether empirical findings support neurocognitive benefits of prescription stimulants. Hence, the primary purpose of this meta-analytic study was to examine the potential effects of prescription stimulants on cognitive functioning of adults with and without ADHD. A systematic search and retrieval process resulted in the calculation of effect sizes from 91 studies. Fourteen meta-analyses were conducted across three levels of constructs, ranging in scope from broad to narrow. Findings indicated significant, but small effect sizes for cognition (g = 0.15), as well as the broad cognitive constructs of abilities of focused behavior (g = 0.14), learning and memory (g = 0.10), and executive function (g = 0.13). Small effect sizes were also revealed for the narrow cognitive constructs of inhibitory control, working memory, processing speed, declarative learning and memory, and self-regulation. Effects were the greatest for declarative long-term memory (g = 0.50) that was assessed 1 to 7 days following drug administration and learning, suggesting that ADHD medication may proffer academic benefits for college students. Studies investigating the effects of ADHD medication on measures of non-declarative memory and planning and decision-making, however, resulted in effect sizes that approached zero. Furthermore, 23 variables (e.g., study design, participant characteristics, medication type) were assessed as potential moderators, but the majority of analyses did not reveal significant differences between outcomes. Of particular note, differences between the neurocognitive effects of ADHD medication on adults with and without ADHD were not supported. These findings suggest that ADHD medication may indeed act as a neurocognitive enhancer, but only for specific domains of cognition. Considering that college students are already engaging in illegal use of prescription stimulants for academic enhancement, as well as the potential for stimulant misuse to have serious side effects and adverse outcomes, these results point to the glaring need for public policy concerning the misuse of prescription stimulant medications.