Purpose: Neurocognitive; to compare memory function in regular ecstasy users with memory function in cannabis-user controls, assessing potential effects of ecstasy use, cannabis use and intelligence on memory function. Design: Retrospective (non-experimental) between-subjects design, with drug use (ecstasy use versus non-ecstasy use) serving as a between-subjects variable, and with all participants assessed on memory and intelligence and completing drug use histories and measures of psychological and somatic symptoms.

Subjects: 40 ecstasy users (of 47) and 37 cannabis users (of 37) probably residing in the Sydney (Australia) area and recruited via advertisements in local music magazines and flyers posted around the University of New South Wales. Matching - No matching explicitly mentioned; groups appear to be matched on gender, education, alcohol and cannabis use, and approximately matched on age.

Criteria for Inclusion, Ecstasy Users - Self-reported regular ecstasy use for at least 6 months prior to study, with minimum of 1 occasion per month. Cannabis Users - Regular use of cannabis for at least 6 months prior to study, with no apparent minimum frequency of use, and lifetime use of no more than 5 ecstasy tablets. All groups - No regular use of illicit drugs other than ecstasy or cannabis, not taking prescription psychoactive medication, mentally healthy (excepting substance abuse or depression), lacking any organic brain disorders (including epilepsy, attention-deficit disorder) as established via clinical interview conducted via telephone), absence of any visual or hearing impairment that would prevent completion of tests, and English as first language. Seven of the originally selected sample of 47 ecstasy users were excluded on the basis of either urinary detection of psychoactive drugs (6) or failure to provide urine sample (1).

Drug Use Parameters - Ecstasy users reported average lifetime consumption of 258 +/- 574 ecstasy tablets (range = 10-3583 tablets), with no information provided on average dose per use. Excluding the highest lifetime dose, the average lifetime consumption was 89 tablets. (Estimated dose, using frequency, days divided by frequency, quantity = 1.95 tablets per use). Average duration of ecstasy use, in months, was 45.9 +/- 37.6 months (range = 8-154), and average frequency of use as times per month, was approximately 2.4 times (days per month), with a range of 0-13 days per month). Number of tablets used per month, on average, was 4.7 +/- 7.1 (range = 0.5-34.4). Average time since last use, in days, was 18.4 +/- 28.9 days, range = 3-180 days). Average lifetime consumption of ecstasy in the cannabis user group was 1.6 tablets. Other Drugs - Reported as number of participants/entire sample reporting regular use and average dose per month. Alcohol was used by 39/40 ecstasy users (71.4 +/- 91 units per month, and by 35/37 cannabis users, 74.9 +/- 87.7 units per month. Cannabis was used by 25/40 ecstasy users, at 67.9 +/- 258.6 joints per month, and by 37/37 cannabis users, at 62.6 +/- 119.2 joints per month. Amphetamines were used by 21/40 ecstasy users, at 0.5 +/- 1.1 g per month, and by none of the cannabis users. Cocaine was used by 7/40 ecstasy users, at 0.2 +/- 0.5 g per month, and was used by none of the cannabis users. Heroin was used by 3/40 ecstasy users, at 0.3 +/- 1.2 "hits", and by none of the cannabis users. LSD was used by 4/40 ecstasy users, at 0.2 +/- 0.6 doses per month, and by none of the cannabis users. Benzodiazepines were used by 4/40 ecstasy users, at 0.1 +/- 0.4 doses per month, and by none of the cannabis users. Inhalants (nitrous oxide and amyl nitrate only) used by 5/40 ecstasy users, at 5.9 +/- 22.4 doses, and by none of the cannabis users. Ecstasy users were more likely to use drugs other than alcohol or cannabis regularly.

Group Demographics and Matched Variables - Groups were not formally matched on any one variable, but appear to be similar in education, gender composition, and use of alcohol and cannabis. Gender - (reported as percentage) As M/F ratio, Ecstasy users = 18/22 (45% male), and for cannabis users, 19/18 (51%). Age - Average age of ecstasy users was 25.3 +/- 6.5 years, and average age of cannabis users was 23.2 +/- 5.9 years. Education - (Reported as average of 4-point scale, wherein 1 = 10 years, 2 = 11 years, 3 = 12 years and 4 = current or completed tertiary (university) education). Ecstasy users had attained approximately 13 +/- 1 year of education (3.5 +/- 1), and cannabis users also had attained approximately 13 +/- 1 year of education (3.5 +/- 1). Other variables - Average vocabulary score of ecstasy users was 11.33 +/- 2.7, and for cannabis users was 13.19 +/- 2.1.

Measures: Intelligence - Assessed via Kaufman Brief Intelligence Test (K-BIT), and vocabulary assessed via the WAIS vocabulary test.

Memory - Assessed via Wechsler Memory Scale (WMS), which includes 8 scales; auditory and visual memory, immediate and delayed memory and working memory and global memory score.

Health - Self-reported psychological and somatic symptoms were assessed via the Symptom Checklist-90-Revised (SCL-90-R). Self-reported physical and psychological well-being was measured through the SF-36, containing 8 scales, including scales for physical health, mental health and general health.

Analysis: Intelligence - Differences between ecstasy users on vocabulary and intelligence were examined by performing student's t-tests, with drug use (ecstasy user versus cannabis user) serving as the between-group variable and with p. value set at 0.05.

Memory - Group differences in memory were assessed via student's t tests, with drug use (ecstasy user versus cannabis user) serving as between-group variable, and with p. value set at 0.05. Fully planned multiple linear regressions were used to examine performance on each of the eight scales of the WMS, with age, gender, vocabulary scale, (log transformed) lifetime ecstasy exposure, use of amphetamines, frequency of cannabis and cocaine use as factors and each sub-scale score as a dependent measure. Because 12/40 ecstasy users and 12/37 cannabis users had positive urine screens for THC or metabolites, an additional comparison (unspecified, perhaps student's t) with urine screen results (positive versus negative for THC or metabolites) serving as a between-group variable.

Health - Scores on both measures of self-reported psychological and physical health compared by student's t tests, with drug use group (ecstasy user versus cannabis user) as the between-group variable, with p. value set at 0.05.

Results - Significant Differences Found: Intelligence - Ecstasy users had significantly lower vocabulary scores than cannabis users, at p. = 0.001. Memory - Vocabulary was the only significant predictor of immediate auditory memory scores. Frequency of cannabis use predicted poorer visual memory scale scores. An adjusted model found vocabulary to be a significant predictor of immediate memory performance. Auditory delayed memory was best predicted by age and by vocabulary, with age effects unspecified. Auditory recognition memory was best predicted by gender (males performing better), age and vocabulary, with effects of age not specified. "Working memory" scores were best predicted by vocabulary and amphetamine use. Vocabulary score was the only significant predictor of general memory scale scores.

Health - Ecstasy users reported greater problems on 4 of the 8 scales of the SF-36, including "physical functioning," "bodily pain," "physical role" and "general health."

Results - No Significant Differences: Intelligence - Ecstasy users and cannabis users scored similarly on the K-BIT.

Memory - Ecstasy users did not have significantly different scores on any of the 8 WMS sub-scales. There was a trend for ecstasy users to perform less well in auditory immediate and delayed sub-scales. People with and without positive urine screens for THC or metabolites did not perform significantly differently on the memory sub-scales. There were no significant predictors of visual delayed memory. There was only a trend for frequency of cannabis to affect immediate memory scores, with more frequent use associated with lower scores.

Health - Ecstasy users and cannabis users did not have significantly different SCL-90-R scores, indicating similar levels of self-reported psychological health. Ecstasy users and cannabis users did not differ in their scores on 4 of 8 SF-36 scales; "vitality," "social function," "emotional role" and "mental health."

Overall Effects: A comparison of memory function, as assessed via WMS, in ecstasy users and cannabis user controls failed to find differences in memory function attributable to ecstasy use. There was a trend for ecstasy users to have lower scores on immediate and delayed auditory memory scales. However, as well as failing to reach statistical significance, it appears that vocabulary (for both immediate and delayed memory) and age (in delayed score only) were better predictors of performance. Regression analyses employing age, gender, vocabulary, and use of other drugs (cannabis, amphetamines and cocaine) as variables as well as lifetime ecstasy use, found that vocabulary was a stronger predictor of performance on WMS scales than any other variable. Age, gender, cannabis user and amphetamine use each predicted performance on one or more memory scale. When the SCL-90-R was used as a measure of self-reported health, no differences were found between ecstasy users and cannabis users. However, ecstasy users did have lower scores on 4 of 8 scales on another self-reported health measure, with 3 of 4 scores relating to reported physical health, and not mental health.

Comments: This paper is one of the first reports of memory function and self-reported health in fairly similar samples of ecstasy users and cannabis users. As has been the case with other studies (e.g. Bolla et al. 1998; Semple et al. 1999), and unlike another study (Rodgers 2000), this research found that the two groups did not perform differently on the WMS. In this case, ecstasy use did not explain a significant amount of variance in memory performance, (assuming the authors analyzed data as each variable was removed). In contrast, a longitudinal study comparing memory at baseline and a year later in a group of ecstasy users found significant reductions in RBMT memory scores, especially "story" scores (Zakzanis and Young 2001). The authors of this report acknowledge that some ecstasy use was reported in their cannabis user group, but also note that if ecstasy use affects memory, a difference still should have been seen, given that ecstasy users had taken far more ecstasy. Overall, these study findings suggest memory in drug users may be influenced by a number of demographic and drug use parameters, and that these factors (such as age, gender, frequency of cannabis use and amphetamine dose) may independently influence different aspects of memory, Failure to find differences in SCL-90-R scores, a finding similar to results recently reported by others (e.g. Daumann et al. 2001; Morgan et al. 2002) indicates that general drug use or cannabis use, and not ecstasy use, is associated with changes in self-reported psychological health. The causal relationship between drug use and psychological health remains unclear, especially given some findings that prior psychiatric diagnosis predicts subsequent drug use (Lieb et al. 2002). Because the study is retrospective and participants are self-selected on the basis of drug use, findings are not readily generalizable to the population as a whole, and the sample size is relatively small, though larger than samples employed in other studies.