Purpose: Neuropsychological, self-reported cognitive function: to investigate prospective memory function in a large number of ecstasy users and non-users via a web-based administration of measures of self-reported memory, and an examination of the relative contributions of ecstasy use and cannabis use to memory function.

Design: Non-experimental (retrospective) design, with use of ecstasy serving as one predictor and use of cannabis serving as another predictor. All participants completed on-line surveys of drug use and measures of self-reported memory function.

Subjects: 155 ecstasy users and 192 cannabis users (categories non-exclusive), with respondents residing in the Europe or North America. These respondents part of a pool of 490 respondents. Respondents were recruited through various means, including placing announcements about the website on relevant e-mail lists and groups, postings on other web pages and announcements at the researchers' university, and e-mailed personal communications. Matching - No attempt has been made to explicitly match ecstasy users and non-ecstasy users.

Criteria for Inclusion, Ecstasy users - Reporting having used ecstasy at least once during a lifetime. Non-ecstasy users - Reporting never having used ecstasy. Cannabis use - (in both ecstasy users and non-users) - Reporting having used cannabis at least in lifetime. All groups - Having completed all measures at the website, absence of signs of mischievous completion (i.e. grossly discrepant demographic information, self-reported intoxication during time of measure completion), and belonging to only one IP address (to reduce or eliminate effects of multiple completions from the same individual). While not an explicit criterion, fluency in English probably needed to complete all instruments.

Drug Use Parameters - Ecstasy use was self-reported in 155 of 490 respondents. 69 reported lifetime use of 1 to 9 ecstasy tablets, 66 respondents reported lifetime use of 10-99 ecstasy tablets and 20 respondents indicated lifetime use of at least 100 ecstasy tablets. No information is provided about average dose per use, duration of use, frequency of use and time since last use. 192 respondents reported cannabis use. Of these 192 respondents, 91 reported smoking 1-4 joints per month or less, 48 reported smoking 5-20 joints a month, and 53 reported smoking at least 21 joints per month. No information is provided concerning lifetime (or yearly) cannabis use or duration of use. Of all ecstasy users, 46/155 reported little or no use of cannabis, and of all cannabis users, 83/192 reported never having used ecstasy. Data on use of other drugs was collected but not included in analyses, and results not provided in this report.)

Group Demographics and Matched Variables - The authors did not match ecstasy users on any variable. Demographic data is presented for the sample as a whole, and has not been broken down by presence versus absence of ecstasy use. Gender - as M/F ratio, 193/297. Age - Reported here as modal age was 21-25, with 75.5% (372/490). Education - Presented as highest point of qualification, with 25.1% having completed high school or less, or having left this item unanswered (123/490) (approximately 12 years education), 32% (157/490) enrolled in a college or university (approximately 14 years education) (24.5% (121/490) had an undergraduate degree (approximately 16 years education) and 18.4% had at least some post-graduate education (90/490) (approximately 18 years education). Geographical Location - Most respondents were either residing in Europe; 79.4%, (387/490) or the US, 16.1% (79/490), with only 5.5% (27/490) residing outside these areas or leaving this item unanswered. Occupational Status - 53.5% (262/490) of respondents indicated they were students, and 36.9% (181/490) indicated they were employed, and 9.6% (47/490) reported they were unemployed/retired, or didn't answer this question.

Measures: Drug Use (used for demographics) - Modified on-line form of the UEL Recreational Drug Use Questionnaire, with drug descriptions made more comprehensible internationally (i.e. outside the UK).

Memory - Self-reported lapses in memory (retrospective) assessed with Everyday Memory Questionnaire (EMQ), 27-item self-report measure with responses made by indicating frequency of each lapse by checking corresponding number.

Prospective Memory - Assessed via the Prospective Memory Questionnaire (PMQ), a self-report questionnaire, also using Likert-type scale to indicate likelihood of occurrence in set period of time. The PMQ has 3 scales; short-term habitual prospective memory (e.g. forgetting to turn off alarm clock after waking), long-term episodic prospective memory (e.g. forgetting to pass on a message to someone) and internally cued prospective memory (e.g. forgetting what one intended to say mid-sentence). In addition, PMQ has "memory strategies" scale.

Impulsivity/Prospective Memory - Number of times an incomplete questionnaire was submitted was measured, with errors indicating impulsivity, impaired planning or prospective memory.

Analyses: Reliability - EMQ and PMQ tested for reliability, with PMQ scales treated separately.

Memory - Separate linear regression analyses were conducted with extent of ecstasy use (in total number of tablets), extent of cannabis use (in use of joints per month), and PMQ strategies scale score serving as predictors, and each memory scale score as the dependent measure. Separate analyses were scored for EMQ, PMQ-short term habitual, PMQ-long-term episodic, PMQ-internally cued, and number of errors made during questionnaire completion. Those reporting use of only 1 drug (ecstasy or cannabis), and not the other were excluded from regression.

Association Between Ecstasy and Cannabis Use - Spearman's rho (ranked correlation coefficient) performed to examine association between use of ecstasy and use of cannabis.

Results - Significant Differences Found: Association between Ecstasy Use and Cannabis Use - Use of ecstasy and use of cannabis were strongly associated, though (as indicated in "Drug Use Parameters") there were respondents who reported using one substance but not the other.

Reliability - Reliability was highest for EMQ, and lowest for PMQ-short term (habitual). All scales except PMQ-short term had reliability above 0.80. Memory - PMQ-strategies was negatively associated with both ecstasy use and cannabis use; hence future regressions included it as a predictor/covariate. Cannabis use was found to be a unique predictor of EMQ scale score, with cannabis use associated with lower EMQ scale scores. Cannabis use was also associated (though less strongly) with PMQ-internally cued and PMQ-short term habitual scores, with lower scores predicted by extent of cannabis use. Ecstasy use significantly predicted PMQ-long term episodic scores, with lower scores associated with greater extent of use. Ecstasy also predicted number of errors made in completing questionnaires, though less strongly than association with PMQ-long term episodic scores, with ecstasy associated with increased number of errors.

Results - No Significant Differences: Memory - Cannabis use did not significant predict PMQ-long term episodic memory. Ecstasy use did not significantly predict EMQ score, or PMQ scores for short term or internally cued prospective memory.

Overall Effects: In a survey of self-reported memory and planning impairment conducted on-line, ecstasy use and cannabis use were both associated with increased self-reports of memory failure, but in different domains. Cannabis use was associated with an increase in self-reported difficulties in short-term retrospective memory, as measured through EMQ. Cannabis use was also associated with increased self-reported difficulties in remembering to perform or complete frequently performed tasks (PMQ-habitual) and with internally-cued prospective memory. The association between cannabis use and EMQ scores was stronger than that between cannabis use and PMQ scores. In contrast, ecstasy use was strongly associated with increased self-reported difficulties in remembering to complete or carry out specific tasks (or difficulty in following plans), as measured through PMQ-long-term episodic. Ecstasy use was also associated with number of errors made in completing the survey, though this association was not as strong as that between ecstasy use and PMQ-long-term episodic scores. The effects of ecstasy use and cannabis use on memory appear to be largely independent of each other. The on-line version of the EMQ is reliable, and 2 of 3 scores on the PMQ were fairly to highly reliable, with one (short term habitual) only moderately reliable (reliability coefficient below 0.7).

Comments: This is the first report describing findings gathered from an on-line study intended to examine the association between drug-use and cognitive function. As the first report of this sort, it has both strong points and weak points. The sample size examined in this report is notably large, and the authors make use of regression analyses to separate the effects of ecstasy use and cannabis use in this population. However, the study is still retrospective, and reliability for the PMQ short term sub-scale was moderate. This means that associations between drug use and this variable may both have been masked or exaggerated by use of a less reliable score. Examination of the construct measured by the PMQ suggests that this measure may be assessing executive function or planning in addition to or instead of memory function. There seems to be some dissociation between self-reported problems attributed to ecstasy and deficits on assessments of cognitive function (Croft 2001; Fox et al. 2001), and this suggests that study findings cannot be considered a direct indicator of drug-induced changes in memory or planning. Ecstasy use and cannabis use may be mediating ability to monitor cognitive failures or motivation to report them to others instead of or in addition to actual instances of failed memory or planning. Since a large majority of ecstasy users also use cannabis, the findings here suggest that ecstasy use may not be the only contributor to impaired memory and/or executive function found in studies comparing regular ecstasy users to non-user controls.