Neurocognitive enhancement or impairment? A systematic meta-analysis of prescription stimulant effects on processing speed, decision-making, planning, and cognitive perseveration.

Abstract

Increasing numbers of adults, particularly college students, are misusing prescription stimulants primarily for cognitive/academic enhancement, so it is critical to explore whether empirical findings support neurocognitive benefits of prescription stimulants. Previous meta-analytic studies have supported small benefits from prescription stimulants for the cognitive domains of inhibitory control and memory; however, no meta-analytic studies have examined the effects on processing speed or the potential impairment on other domains of cognition, including planning, decision-making, and cognitive perseveration. Therefore, the present study conducted a meta-analysis of the available literature examining the effects of prescription stimulants on specific measures of processing speed, planning, decision-making, and cognitive perseveration among healthy adult populations. The meta-analysis results indicated a positive influence of prescription stimulant medication on processing speed accuracy, with an overall mean effect size of g = 0.282 (95% CI 0.077, 0.488; n = 345). Neither improvements nor impairments were revealed for planning time, planning accuracy, advantageous decision-making, or cognitive perseveration; however findings are limited by the small number of studies examining these outcomes. Findings support that prescription stimulant medication may indeed act as a neurocognitive enhancer for accuracy measures of processing speed without impeding other areas of cognition. Considering that adults 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, the establishment of public policies informed by interdisciplinary research surrounding this issue, whether restrictive or liberal, is of critical importance.

Prescription stimulant medication misuse: Where are we and where do we go from here?

“…Nonetheless, findings from this study are notable in that significant and small effects of amphetamine were found to benefit processing speed (Marraccini et al, in press). …”

“…Preliminary findings from a meta-analysis examining the neurocognitive effects of prescription stimulants cognitive flexibility (Marraccini et al, in press), however, did not support Advokat’s (2010) conclusions about impairments of cognitive flexibility. Although limited by a small number of studies ( k = 6), results suggested that amphetamine and methylphenidate did not result in significant effects on cognitive perseveration.…”

“…A limited number of studies have attempted to address this question and results from three systematic meta-analyses (Ilieva, Hook, & Farah, 2015; Marraccini, Weyandt, Rossi, & Gudmundsdottir, in press; Repantis, Schlattmann, Laisney, & Heuser, 2010) and two reviews (Advokat, 2010; Smith & Farah, 2011) have also revealed small to moderate effects on behavior, with the greatest effects associated with long-term memory. As presented in Table 1, these studies investigated a variety of stimulant medication types and participants that differed on a number of dimensions, resulting in findings that both overlap and differ depending on the study design inclusion requirements.…”

“…Although only one of the included studies (Marraccini et al, in press) examined the effects of prescription stimulants on processing speed, it is important to note that many of the previously described constructs may have considerable overlap with processing speed (e.g., trail making tasks, response time tasks, etc.). Nonetheless, findings from this study are notable in that significant and small effects of amphetamine were found to benefit processing speed (Marraccini et al, in press).…”

“…All of the review and meta-analytic studies included studies that examined cognitive effects of methylphenidate and/or amphetamine across any dose level; however, the majority of studies included in these studies used doses that ranged between 10–20 mg for both drug types. Both Ilieva et al (2015) and Marraccini et al (in press) included dose level (low versus high) as a moderator variable of interest. Among the constructs examined in these studies, only delayed episodic memory demonstrated significantly different results based on dose.…”