Purpose: Neurocognitive; To investigate the long term effects of ecstasy use on attentional processes, and to examine whether one or more parameters of ecstasy are associated with any changes in attentional processes seen in ecstasy users.

Design: Retrospective (non-experimental) between-subjects design, with drug use (ecstasy use versus no ecstasy use) as a between-subjects factor, wherein all participants completed assessments of intelligence and attention.

Subjects: 24 ecstasy users and 30 polydrug users, probably residing in or near Toronto (Ontario). No information is provided on participant recruitment, but previous reports by the same authors (Zakzanis and Young 2001) reported that ecstasy users and controls were recruited via word of mouth (staff referrals). Matching - Groups matched on age, education and approximately matched on gender.

Criteria for Inclusion - Ecstasy Users - Reported having used ecstasy at least once. Non-Ecstasy users - Reported never having used ecstasy, but use of other drugs was permitted. Both groups - Not pregnant, no past or current major medical or psychiatric illness, as assessed through medical interview, no current alcohol dependence, absence of current dyslexia, migraine or eating disorder, and fluent English-speaker. Abstinence from all psychoactive drugs for at least 2 weeks prior to the study day, with abstinence verified through urinalysis and analysis of blood on study day. Having reported sleeping for 7-9 h each night for at least a week prior to study day.

Drug Use Parameters - Average number of times ecstasy was used in a lifetime was 22.3 times (range = 2-100), with an average dose per use of 1.3 tablets (Range = 0.5-2 tablets). Average duration of ecstasy use, in months, was approximately 12.6 months (range = 6-144 months), and average frequency of use was 1.7 times per month (range = 0.5-4 times per month). Time elapsed from last ecstasy use to study day was reported as 180.2 days (Range = 14-120 days). Other drug use - Use of other drugs for ecstasy users and controls reported as number of people in each condition reporting some use of each substance. Amphetamine was used by 6/24 ecstasy users and 6/30 non-ecstasy users, cocaine was used by 5/24 ecstasy users and 7/30 non-ecstasy users, benzodiazepines were used by 1/24 ecstasy user and none (0/30) of the non-ecstasy users, LSD and other hallucinogens were used by 13/24 ecstasy users and by 8/30 non-ecstasy users, cannabis was used by 20/24 ecstasy users and by 16/30 controls, solvents were used by 3/24 ecstasy users and by 1/24 non-ecstasy user, opiates were used by 7/24 ecstasy users and by 1/30 non-ecstasy user, PCP and related drugs were used by 4/24 ecstasy users and by 3/30 non-ecstasy users, alcohol was used by 23/24 ecstasy users and by 25/30 non-ecstasy users and nicotine was used by 18/24 ecstasy users and 12/30 non-ecstasy users.

Group Demographics and Matched Variables - Though the authors do not explicitly state intent to match groups, ecstasy users and controls appear to be matched on age, education, and (approximately) on gender and use of other drugs. Gender, as M/F ratio - Ecstasy users, 11/13, non-ecstasy users, 15/15. Age - The average age of ecstasy users was 22.7 +/- 3.7 years, and average age of non-ecstasy users was 22.5 +/- 5.2 years. Education - On average, ecstasy users had attained 15.7 +/- 0.8 years of education, and non-ecstasy users had attained an average of 15.7 +/- 1 years of education. Other Drugs - While similar numbers of ecstasy users and non-users reported using most other drugs, an informal examination of data suggests that ecstasy users were more likely to use cannabis and hallucinogens when compared to non-ecstasy users.

Measures: Intelligence/Cognitive Function - Assessed via the Wechsler Abbreviated Scale of Intelligence (WASI), consisting of a test of vocabulary (verbal IQ) and matrix reasoning (performance IQ).

Attention - Attentional processes were assessed via the Test of Everyday Attention (TEA), a measure consisting of 8 sub-tests; Map Search 1 and 2 (circle symbols (e.g. restaurants, gas stations) on map in 1 min (1), circle additional symbols for an additional 1 min (2), Elevator Counting (count number of tones), Elevator Counting with Distractions (count tones, ignore differently-pitched tones), Visual Elevator (count number of visually presented elevator icons, change directions on arrow cue), Elevator Counting with Reversal (Count middle-pitch tones, use low and high-pitched tones as direction reversal cues (e.g. up or down), Telephone Search (circle symbols embedded in names or listings in telephone book), Telephone Search While Counting (Circle symbols in telephone book while counting tones (same used in "Elevator Counting"), paying equal attention to both tasks).

Analyses: Cognitive function and attention - Ecstasy user and non-ecstasy user scores on all tests were compared using student's t tests, with p. value set at 0.05. Effect size (strength of effect exerted on one variable by another) was calculated as well, with ecstasy use serving as subject variable).

Drug Use Parameters and Test Scores - Correlational analyses were performed on all test scores (WASI and all TEA sub-scales), and each drug use parameter. However, data is only presented for correlations between total lifetime dose and for estimated dose per use, suggesting that only these two drug use parameters were correlated with WASI or TEA performance.

Results - Significant Differences Found: Tests of Intelligence / Neurocognitive Function - None found

Attention - Ecstasy users had lower scores on the Map Search 2 component of the TEA when compared with non-ecstasy users.

Drug Use Parameters and Test Scores - Performance on Map Search 1, Visual Elevator (Accuracy), and Elevator Counting with Reversals were inversely associated with dosage (either dose per use, or dose per use x occasions of use, as done in Bolla et al. 1998). Test scores on these sub-tests declined with increasing ecstasy dosage. Performance on Telephone Search While Counting was inversely associated with number of tablets used overall, with test scores on this TEA subtest declining as overall number of tablets used increased.

Results - No Significant Differences: Tests of Intelligence / Neurocognitive Function - Ecstasy users and non-ecstasy users did not differ significantly in scores on either the Vocabulary or the Matrix Reasoning sub-test of the WASI.

Attention - Ecstasy users and non-ecstasy users did not have significantly different scores on all other TEA sub-scales (Map Search 1, Elevator Counting, Elevator Counting with Distractors, Visual Elevator, Elevator Counting with Reversals, Telephone Search, Telephone Search While Counting). Drug Use Parameters and Test Scores - Vocabulary and Matrix Reasoning scores were unrelated to drug dosage (either average dose per use or dose per use x number of occasions) or to total number of tablets taken. Scores on the TEA Map Search 2, Elevator Counting, Elevator Counting with Distraction, Visual Elevator (total score), and Telephone Search were neither positively nor negatively associated with either ecstasy dosage or total number of tablets taken. Map Search 1, Visual Elevator (Accuracy) and Elevator Counting with Reversals were not associated with total (lifetime) number of ecstasy tablets used, and Telephone Search While Counting scores were not associated with ecstasy dosage.

Overall Effects: 24 ecstasy users and 30 non-ecstasy using controls performed similarly on a measure of attentional processes, excepting performance on 1 of 8 sub-tests (Map Search 2), wherein ecstasy users performed worse than non-ecstasy users. Differences in performance cannot be attributed to differences in gender or age, as groups were matched on these variables, and all participants reported getting at least 7 h sleep per night for a week prior to the study day. Performance on a measure of vocabulary and non-verbal (matrix) reasoning were also similar in ecstasy users and non-ecstasy. However, total number of ecstasy tablets taken was inversely related to performance on Telephone Search While Counting, a sub-test of divided attention, with total number of tablets consumed inversely associated with task performance. Performance on 3 of 8 tasks (Map Search 1, Visual Elevator (Accuracy) and Elevator Counting with Reversals all declined with increasing ecstasy dosage, probably referring to average dose per use, but possibly to estimated cumulative dosage. The authors conclude that their result indicate that ecstasy use or a related variable associated with ecstasy use may alter specific attentional processes without altering the majority of attentional processes.

Comments: While most studies have assessed attention in the context of a full neurocognitive battery (McCann et al. 1999; Gouzoulis-Mayfrank et al. 2000), this is the first paper to focus on attentional processes in ecstasy users. As with research previously reported by this team (Zakzanis et al. 2001; Zakzanis and Young 2001), pains were taken to match participants on several dimensions and to reduce the effects of poor sleep habits by requiring that all participants have at least a week of sleep. As was the case with a previous report assessing executive function in ecstasy users (Zakzanis and Young 2001), there are some puzzling discrepancies in findings, wherein no relationship is found between any of the drug use parameters and the one sub-test of attention that differentiated ecstasy users from non-users. Such a discrepancy raises the question as to whether differences between ecstasy users and non-ecstasy users are at least partly due to group differences in some other variable, such as cannabis use or a presence of a pre-existing condition. It is also interesting that ecstasy users had lower scores than non-ecstasy users on a relatively simple test of sustained attention rather than showing deficits on more complex tests assessing attentional switching or attention to multiple modalities. It is difficult to imagine a deficit in a simple attentional process that does not affect performance on more complex tasks, unless the functions needed to perform the other tasks are relatively independent of each other. Study limitations include retrospective design (particularly disappointing in research from a team that performed one of the few time-series studies in the field), potential selection biases and differences in use of drugs other than ecstasy.