Prospective memory impairment in abstinent MDMA ("Ecstasy") users

Recreational drug use and prospective memory

Prospective memory (PM) impairment in recreational drug users has been documented in recent years. However, most studies on the effects of drugs on PM contain several methodological challenges, such as small sample size (< 100 participants), unrepresentative sample type (e.g., student or patient), short abstinence period (< 7 days), and lack of control of potential confounds (e.g., sleep and IQ). The present study investigated the possible consequences of recreational drug use on prospective memory, using self-report and lab-based prospective memory measures while overcoming the methodological challenges. The sample was composed of 47 non-users (27 females, age range from 18 to 50 +) and 53 drug users (21 females, age range from 18 to 50 +). Recreational drug users reported significantly more deficits in the long-term episodic, short-term habitual, and internally cued PM failures subscales of the Prospective Memory Questionnaire. However, these deficits were eliminated after controlling for covariates (e.g., age, sleep quality, general health, alcohol usage). Recreational drug users also performed worse than non-users in the short-term, long-term, event-based, and time-based PM subscales of the Royal Prince Alfred Prospective Memory Test. These results remained significant after controlling for the covariates. Drug users demonstrated greater impairments on time-based and long-term PM tasks thought to be linked with executive functioning. Taken together, the present study provides further support for recreational drug-related deficits in PM and highlights a dissociation between self-report and lab-based PM measures.

Illegal drug use and prospective memory: A systematic review

Illegal drug use is proposed to interfere with neurobiological functioning by damaging the neurotransmitter communication systems that are believed to be responsible for cognitive abilities, including perception, attention, and memory. This review specifically examined effects of illegal drug use on prospective memory (PM) - memory for future actions. Twenty- seven studies spanning 14 years were included in this review which were divided into two broad categories based on testing methods used: self-report and lab-based testing methods. The quality of the included studies was assessed across five categories: sample type, sample size, abstinence period, testing methods and control for confounding factors. The overall quality of evidence was good for six studies and moderate for sixteen studies and low for five studies. The results from the studies employing self-report were inconsistent as illegal drug users exhibited PM deficits in some studies, but not in others. However, the studies with lab-based testing methods demonstrated more consistent findings with illegal drug users scoring worse than non-users on various PM tests. There were also consistent findings on the link between the dosage of drug taken and level of PM deficit. Based on the literature, there is moderate evidence that illegal drug use impairs PM ability. We recommend that further lab-based studies be conducted to assess dose-response effects on drug-specificity.

The effects of licit and illicit recreational drugs on prospective memory: a meta-analytic review

RATIONALE

There are no recent reports summarising the magnitude of prospective memory (PM) impairments in recreational drug users.

OBJECTIVE

We performed a meta-analysis of studies (with a parallel group design) examining PM performance in users of common recreational drugs (including alcohol and tobacco) who were not intoxicated during testing. Studies were also evaluated for the presence of methodological bias.

METHODS

Twenty-seven studies were included in the meta-analysis following literature searches of MEDLINE, EMBASE and PsycINFO. Effect sizes (standardised mean difference; SMD) were calculated separately for the effects of alcohol, cannabis, ecstasy, methamphetamine and tobacco use. The influences of drug use and study characteristics on effect sizes were explored using meta-regressions. Sources of study bias were also assessed.

RESULTS

Heavy drinkers and regular drug users tended to perform worse than controls on event and time-based PM tasks. Effect sizes (standardised mean differences; SMDs) for event-based PM impairment across the different drug-using groups/heavy drinkers ranged between - 1.10 and - 0.49, with no 95% CI crossing 0.00. SMDs for time-based PM ranged between - 0.98 and - 0.70. Except for the CIs associated with the ES for smokers' time-based PM performance, no CIs crossed 0.00.

CONCLUSIONS

Although all drug-using groups showed moderate-large impairments in event and time-based PM, effect sizes had low precision and moderate-high levels of heterogeneity. In addition, several methodological and reporting issues were identified in the majority of studies. As such, considerable uncertainty remains regarding the role of confounds and the magnitude of PM impairments in non-intoxicated recreational drug users.

Everyday and prospective memory deficits in ecstasy/polydrug users

The impact of ecstasy/polydrug use on real-world memory (i.e. everyday memory, cognitive failures and prospective memory [PM]) was investigated in a sample of 42 ecstasy/polydrug users and 31 non-ecstasy users. Laboratory-based PM tasks were administered along with self-reported measures of PM to test whether any ecstasy/polydrug-related impairment on the different aspects of PM was present. Self-reported measures of everyday memory and cognitive failures were also administered. Ecstasy/polydrug associated deficits were observed on both laboratory and self-reported measures of PM and everyday memory. The present study extends previous research by demonstrating that deficits in PM are real and cannot be simply attributed to self-misperceptions. The deficits observed reflect some general capacity underpinning both time- and event-based PM contexts and are not task specific. Among this group of ecstasy/polydrug users recreational use of cocaine was also prominently associated with PM deficits. Further research might explore the differential effects of individual illicit drugs on real-world memory.

Assessing the functional significance of ecstasy-related memory deficits using a virtual paradigm

RATIONALE/OBJECTIVES

Previous research shows that the use of ecstasy results in working memory and executive impairments in some users. The present study sought to assess the functional significance of such deficits using a virtual reality task.

METHODS

Twenty-three ecstasy-polydrug users and 26 nonusers were recruited. Individuals completed a drug use questionnaire measures of sleep quality and fluid intelligence. Participants also completed a virtual reality executive function task in which they play the role of an office worker for the day completing predefined tasks such as prioritising different activities according to their importance, organising the physical office environment and managing the outgoing mail in accordance with a delivery schedule.

RESULTS

MANOVA revealed that ecstasy users performed worse on the virtual reality task overall, and this was due to poorer performance on the planning and selection subscales. Contrary to expectations, ecstasy-polydrug users performed better on the time-based prospective memory subscale. Indices of ecstasy use were correlated with the planning subscale of the virtual task.

CONCLUSIONS

The present study provides further support for ecstasy/polydrug related deficits in executive functioning. As it is possible that this task is more ecologically valid and relevant to day-to-day activities of many users, previous research finding null results on executive function tasks may have underestimated the impact of ecstasy-polydrug use on executive functioning.

Involvement of inferior parietal lobules in prospective memory impairment during acute MDMA (ecstasy) intoxication: an event-related fMRI study

Prospective memory refers to the realization of delayed intentions. Several studies have shown that 3,4-methylenedioxy-methamphetamine (MDMA) users perform worse on measures of prospective memory as compared to nondrug users. Interpretation of these data may be limited because of polydrug use, psychosocial stressors, and increased psychopathology that have been reported in MDMA users. This study was designed to directly assess the pharmacological effect of MDMA on prospective memory and brain activity in a double-blind, placebo-controlled, cross-over study. Twelve recreational MDMA users received MDMA 75 mg and placebo and performed an objective prospective memory task during functional imaging. During prospective memory task performance subjects were engaged in a foreground task that consisted of a simple reaction time to visual stimuli (Go trials) and a prospective task of withholding a response during trials that were part of a dynamic memory set (No go trials). Behavioral data showed that a single dose of MDMA increased prospective memory failures in the No go trials, and that number of prospective memory failures was positively correlated to MDMA concentration in plasma. Functional imaging showed that MDMA decreased BOLD activation during Go trials in the thalamus (left), putamen (left), precuneus (left), and the inferior parietal lobules (bilateral), as compared to placebo. During No go trials, MDMA reduced BOLD deactivation in the inferior parietal lobules (bilateral), as compared to placebo. It is concluded that the loss of deactivation in inferior parietal lobules may account for increments in memory failures observed during MDMA intoxication.

Recreational ecstasy use and the neurotoxic potential of MDMA: current status of the controversy and methodological issues

The controversy over possible MDMA-induced serotonergic neurotoxicity in human recreational ecstasy users is examined critically in light of recent research findings. Although the designs of such studies have improved considerably since the 1990s, the evidence to date remains equivocal for a number of reasons, including (1) inconsistent findings on the existence and reversibility of persistent ecstasy-related serotonergic and cognitive deficits; (2) lack of clear association between changes in brain imaging measures and functional deficits attributed to MDMA-induced neurotoxicity; (3) the contribution of concomitant cannabis or other drug use to both brain imaging abnormalities and cognitive deficits; (4) methodological shortcomings such as failure to adequately match samples of ecstasy users and controls; (5) the questionable relevance of animal models of MDMA-induced neurotoxicity to typical human patterns of ecstasy use; and (6) the potential role of inherent pre-drug deficits in serotonergic systems, impulse control and executive cognitive function that may predispose to excessive use of drugs including ecstasy. Given the retrospective nature of nearly all studies of ecstasy users to date, the controversy over whether MDMA has ever caused neurotoxicity or cognitive deficit in human ecstasy users is likely to continue for some time without resolution.

Prospective memory impairment in former users of methamphetamine

RATIONALE

Considerable research indicates that methamphetamine use is associated with neurocognitive impairment, but no empirical study to date has assessed whether these difficulties extend to memory for future intentions (prospective memory).

OBJECTIVES

The present study assessed prospective performance on a laboratory measure of prospective memory that closely represents the types of prospective memory tasks that actually occur in everyday life and provides an opportunity to investigate the different sorts of prospective memory failures that occur ("Virtual Week").

MATERIALS AND METHODS

Twenty adults with confirmed history of methamphetamine use and dependence, currently engaged in rehabilitation and confirmed to be abstinent for an average period of 6 months, and 20 methamphetamine-naive participants were tested on Virtual Week. Various other aspects of cognitive function were also assessed, including retrospective memory and executive functioning.

RESULTS

Methamphetamine users were significantly impaired on Virtual Week, and these deficits did not vary as a function of specific prospective memory task demands. Of all the cognitive measures, cognitive inhibition shared greatest variance with group effects on the prospective memory measure.

CONCLUSIONS

Prospective memory performance is sensitive to prior methamphetamine use even well into abstinence. Methamphetamine users experience generalized difficulties with prospective memory, suggesting that these deficits are likely to have important implications for day-to-day functioning.

Prospective memory impairment in "ecstasy" (MDMA) users

RATIONALE

Considerable research indicates that "ecstasy" users perceive their memory for future intentions (prospective memory) to be impaired. However, only one empirical study to date has directly tested how this capacity is affected by ecstasy use, and this study provided relatively limited information regarding the extent, scope, or implications of problems experienced.

OBJECTIVES

The present study assessed prospective performance on a laboratory measure of prospective memory that closely represents the types of prospective memory tasks that actually occur in everyday life and provides an opportunity to investigate the different sorts of prospective memory failures that occur ("Virtual Week").

METHOD

Ecstasy user group (27 current users and 34 nonusers) was between participants, and prospective memory task (regular, irregular, time-check) was within participants. A measure sensitive to specific aspects of psychopathology was also administered.

RESULTS

Ecstasy users were significantly impaired on Virtual Week, and these deficits were of a comparable magnitude irrespective of the specific prospective memory task demands. The pattern of results was unchanged after controlling for marijuana use, level of psychopathology, and sleep quality. Further, prospective memory was shown to be significantly impaired for both relatively infrequent and relatively frequent ecstasy users, although for the latter group the magnitude of this deficit was greater.

CONCLUSIONS

Prospective memory performance is sensitive to regular and even moderate ecstasy use. Importantly, ecstasy users experience generalized difficulties with prospective memory, suggesting that these deficits are likely to have important implications for day-to-day functioning.

The neuropsychology of ecstasy (MDMA) use: a quantitative review

A growing number of empirical studies have found varying neuropsychological impairments associated with use of 3,4-methylenedioxymethamphetamine (MDMA) use. We set out to determine to what extent neuropsychological abilities are impaired in MDMA users. To do so, meta-analytical methods were used to determine the magnitude of neuropsychological impairment in MDMA users across pre-specified cognitive domains. We found that cognitive impairment secondary to recreational drug use may result in what might be described as small-to-medium effects across all cognitive domains with learning and memory being most impaired. We also found that total lifetime ingestion of MDMA appears to be negatively associated with performance on tasks ranging from attention and concentration to learning and memory. Implications and limitations of these findings are discussed.

Ecstasy (MDMA) and memory function: a meta-analytic update

A meta-analysis was conducted to examine the impact of recreational ecstasy use on short-term memory (STM), long-term memory (LTM), verbal and visual memory. We located 26 studies containing memory data for ecstasy and non-ecstasy users from which effect sizes could be derived. The analyses provided measures of STM and LTM in 610 and 439 ecstasy users and revealed moderate-to-large effect sizes (Cohen's d) of d = -0.63 and d = -0.87, respectively. The difference between STM versus LTM was non-significant. The effect size for verbal memory was large (d = -1.00) and significantly larger than the small effect size for visual memory (d = -0.27). Indeed, our analyses indicate that visual memory may be affected more by concurrent cannabis use. Finally, we found that the total lifetime number of ecstasy tablets consumed did not significantly predict memory performance.