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1999 McCann MDMA Cognition Study
A Review
by Erowid
Cognitive performance in (+/-) 3,4-methylenedioxymethamphetamine (MDMA,"ecstasy) users: a controlled study,
by U.D. McCann; M. Mertl; V. Eligulashvili; G.A. Ricaurte
Psychopharmacology Vol 143, 1999, 417-425




If anyone has comments, further clarifications, or interpretations of this study and its data, we'd love to hear them.

  1. Education
    Why do these people keep doing research studies on mental function where the MDMA users _always_ have significantly less education than the controls? While they argue the difference in education levels don't affect the outcomes, it seems absurd to allow 2 years difference between controls and MDMA users (13.3 years of education for MDMA users and 15.22 for controls). In the US, this represents the difference between little or no college and a couple years of college education.

    A bizarre note in this paper is that despite the fact that these education values are given, the researchers write "There were no differences in the mean educational levels of the two groups." What does this mean?

  2. Dramatic Score Differences
    One notable part of this study is that the data that the researchers do report reflect a large difference between MDMA users and controls. The number correct per minute for the Delayed Recall test were 22.94 for controls and 14.89 for MDMA users (difference of 8 points or 35%) on the first day of testing, although by the third day of testing the gap had narrowed to 28.46 for controls and 25.71 for MDMA users (difference of 2.75 or 10%).

    The differences between the scores for the Serial Add and Subtract (a mildly annoying repetitve task on a computer involving adding and subtracting single digit numbers) were also quite large. The controls scored 36.38 on the first day, the MDMA users scored 28.15 on the first day (a difference of 8.23 or 22%). On the third day the controls scored 61.36 and the MDMA users 40.31 (a difference of 21.05 or 34%).

    These large differences are very concerning, but they may also call the paper's conclusions into question since if these differences are representative of the general population of MDMA users, it seems that such dramatic results would be easy to detect.

    Despite the 20-35% differences in scores on some tests, however, the researchers say that the differences are "quite subtle".

  3. Importance of effects
    Despite the large differences in some scores, the researchers say:
    "DIfferences in cognitive function seen in MDMA users and controls were quite subtle, and only detected using a sensitive battery of cognitive tests. Individuals who took part in the study were generally not aware of having cognitive difficulties, and cognitive impairments were not obvious the investigators."

    Perhaps this battery of tests can suggest a set of simple tests to detect these deficits in larger, less hand-picked populations of users.

  4. Time since last dose
    This study appears better than the others reviewed to date because the average time since last dose for the MDMA users is almost 14 weeks, certainly enough to qualify for medium-term (although the range was 3 weeks to 147 weeks).

  5. Dosage and frequency
    The subjects for this study fall into the heavy use category. The number of exposures varied from 30-725, averaging 215 uses. Their frequency of use averaged to 5.72 uses per month (0.8 to 15) and the usual dose (using an estimate based on 100 mg per dose) averaged to 272 mg ranging from 100 mg to 1000 mg per use. While any problems associated with heavy use are of concern to all users, its hard to say how to relate the experience of someone who has taken MDMA over 700 times at 272 mg per experience to someone who has used it a handful of times at perhaps 100-150 mg.