The relationships of 'ecstasy' (MDMA) and cannabis use to impaired executive inhibition and access to semantic long-term memory

Neurological and cognitive alterations induced by MDMA in humans

3,4 Methylenedioxymethamphetamine generally referred to as MDMA or 'ecstasy' is a ring-substituted phenethylamine stimulant which produces powerful empathogenic effects. Use of MDMA remains popular despite prohibition, and potential long-term negative consequences of repeated use. MDMA produces its acute subjective effects primarily by stimulating the release of serotonin via action at the serotonin transporter (SERT). There is evidence that MDMA administration may lead to long lasting neurotoxic effects on serotonin neurons in primates, and reductions in markers of central serotonin axons, and axon terminals in animals. In humans, demonstration of serotonergic neurotoxicity is much more difficult to identify, and much of the research is complicated by confounding issues of polysubstance use, genetic and environmental factors and reliance on self-reports of previous drug use. We do not review the mechanisms for neurotoxicity in detail as they are covered elsewhere in this special issue. There is a large body of literature, however, which has investigated potential cognitive and neurocognitive consequences of repeated MDMA use. Here we review the literature on cognition, and neuroimaging studies that have investigated structural and functional brain changes associated with ecstasy use.

Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults: A Systematic Review and Meta-analysis

IMPORTANCE

Substantial shifts in perception and policy regarding cannabis have recently occurred, with use of cannabis increasing while its perceived harm decreases. One possible risk of increased cannabis use is poorer cognitive functioning, especially in youth.

OBJECTIVE

To provide the first quantitative synthesis of the literature examining cannabis and cognitive functioning in adolescents and young adults (with a mean age of 26 years and younger).

DATA SOURCES

PubMed, PsycInfo, Academic Search Premier, Scopus, and bibliographies of relevant reviews were searched for peer-reviewed, English-language studies from the date the databases began through May 2017.

STUDY SELECTION

Consensus criteria were used to determine study inclusion through abstract and manuscript review.

DATA EXTRACTION AND SYNTHESIS

This study followed Meta-analysis of Observational Studies in Epidemiology guidelines. Effect size estimates were calculated using multivariate mixed-effects models for cognitive functioning outcomes classified into 10 domains.

MAIN OUTCOMES AND MEASURES

Results from neurocognitive tests administered in cross-sectional studies were primary outcomes, and we examined the influence of a priori explanatory variables on variability in effect size.

RESULTS

Sixty-nine studies of 2152 cannabis users (mean [SD] age, 20.6 [2.8] years; 1472 [68.4%] male) and 6575 comparison participants with minimal cannabis exposure were included (mean [SD] age, 20.8 [3.4]; 3669 [55.8%] male). Results indicated a small overall effect size (presented as mean d) for reduced cognitive functioning associated with frequent or heavy cannabis use (d, -0.25; 95% CI, -0.32 to -0.17; P < .001). The magnitude of effect sizes did not vary by sample age or age at cannabis use onset. However, studies requiring an abstinence period longer than 72 hours (15 studies; n = 928) had an overall effect size (d, -0.08; 95% CI, -0.22 to 0.07) that was not significantly different from 0 and smaller than studies with less stringent abstinence criteria (54 studies; n = 7799; d, -0.30; 95% CI, -0.37 to -0.22; P = .01).

CONCLUSIONS AND RELEVANCE

Associations between cannabis use and cognitive functioning in cross-sectional studies of adolescents and young adults are small and may be of questionable clinical importance for most individuals. Furthermore, abstinence of longer than 72 hours diminishes cognitive deficits associated with cannabis use. Although other outcomes (eg, psychosis) were not examined in the included studies, results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use. Reported deficits may reflect residual effects from acute use or withdrawal. Future studies should examine individual differences in susceptibility to cannabis-associated cognitive dysfunction.

Meta-analysis of executive functioning in ecstasy/polydrug users

Ecstasy/3,4-methylenedioxymethamphetamine (MDMA) use is proposed to cause damage to serotonergic (5-HT) axons in humans. Therefore, users should show deficits in cognitive processes that rely on serotonin-rich, prefrontal areas of the brain. However, there is inconsistency in findings to support this hypothesis. The aim of the current study was to examine deficits in executive functioning in ecstasy users compared with controls using meta-analysis. We identified k = 39 studies, contributing 89 effect sizes, investigating executive functioning in ecstasy users and polydrug-using controls. We compared function-specific task performance in 1221 current ecstasy users and 1242 drug-using controls, from tasks tapping the executive functions - updating, switching, inhibition and access to long-term memory. The significant main effect demonstrated overall executive dysfunction in ecstasy users [standardized mean difference (SMD) = -0.18, 95% confidence interval (CI) -0.26 to -0.11, Z = 5.05, p < 0.001, I 2 = 82%], with a significant subgroup effect (χ 2 = 22.06, degrees of freedom = 3, p < 0.001, I 2 = 86.4%) demonstrating differential effects across executive functions. Ecstasy users showed significant performance deficits in access (SMD = -0.33, 95% CI -0.46 to -0.19, Z = 4.72, p < 0.001, I 2 = 74%), switching (SMD = -0.19, 95% CI -0.36 to -0.02, Z = 2.16, p < 0.05, I 2 = 85%) and updating (SMD = -0.26, 95% CI -0.37 to -0.15, Z = 4.49, p < 0.001, I 2 = 82%). No differences were observed in inhibitory control. We conclude that this is the most comprehensive analysis of executive function in ecstasy users to date and provides a behavioural correlate of potential serotonergic neurotoxicity.

Signs & symptoms of Dextromethorphan exposure from YouTube

Detailed data on the recreational use of drugs are difficult to obtain through traditional means, especially for substances like Dextromethorphan (DXM) which are available over-the-counter for medicinal purposes. In this study, we show that information provided by commenters on YouTube is useful for uncovering the toxicologic effects of DXM. Using methods of computational linguistics, we were able to recreate many of the clinically described signs and symptoms of DXM ingestion at various doses, using information extracted from YouTube comments. Our study shows how social networks can enhance our understanding of recreational drug effects.

Effects of cannabis on neurocognitive functioning: recent advances, neurodevelopmental influences, and sex differences

Decades of research have examined the effects of cannabis on neurocognition. Recent advances in this field provide us with a better understanding of how cannabis use influences neurocognition both acutely (during intoxication) and non-acutely (after acute effects subside). Evidence of problems with episodic memory is one of the most consistent findings reported; however, several other neurocognitive domains appear to be adversely affected by cannabis use under various conditions. There is significant variability in findings across studies, thus a discussion of potential moderators is increasingly relevant. The purpose of this review was to 1) provide an update on research of cannabis' acute and non-acute effects on neurocognition, with a focus on findings since 2007 and 2) suggest and discuss how neurodevelopmental issues and sex differences may influence cannabis effects on neurocognition. Finally we discuss how future investigations may lead to better understanding of the complex interplay among cannabis, stages of neurodevelopment, and sex on neurocognitive functioning.