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1998 Bolla MDMA Memory Study
A Review
by Erowid
Memory impairment in abstinent MDMA ('Ecstasy') users,
by K.I. Bolla; U.D. McCann; G.A. Ricaurte
Neurology Vol 51, Dec 1998, 1532-1537




This study looked for memory problems in 24 MDMA and 24 non MDMA-using controls. The MDMA users reported taking MDMA an average of 60 times (25-300 total uses) at an average dose per use estimated at 158 mg (between 55 mg and 500 mg). The researchers required that the users be abstinent from use for at least 2 weeks and the average period of abstinence at the time of the study was 4 weeks (between 2 and 36 weeks). The users averaged 440 mg per month (between 55 mg and 4000 mg per month used).

The researchers primary finding was:
"MDMA users have impairment in verbal and visual memory [and] the extent of memory impairment correlates with the degree of MDMA exposure".

While the results and conclusions reported by the researchers are very concerning, it seems problematic to rely on this study for any generalizations about the effects on MDMA users. There are several reasons to question the study authors' conclusions.

  1. Contradictory Information
    While we have very little data from this study, one of the pieces they chose to include was displayed in figure 1 (page 1536 of the study). Although the researchers state in their Results that "Greater use of MDMA (total milligrams per month) was associated with greater impairment in ... delayed visual memory (p < 0.06)", this chart shows that this generalization does not even reflect the data as they present it. This figure shows that in the group of MDMA users with lower vocabulary skills, worse "visual memory delayed" scores corresponded to higher monthly intakes of MDMA. But this chart also shows that in the subgroup of MDMA users with higher vocabulary skills, better "visual memory delayed" scores correspond to higher monthly intakes of MDMA. This is directly in opposition to Bolla's statement that increased MDMA intake corresponds to worsening memory of this type. According to this chart, high-vocab MDMA users who took 800 mg or higher per month of MDMA (considered very heavy use) scored better than controls.

  2. We see no data
    The fact that we have none of the uninterpreted data presented and that their analysis of the data (as in the figure 1 analysis above) is fundamentally flawed, it seems absurd to assume that we can trust the results of this study to say anything of value without independent re-analysis of the underlying data. The large chart presented in the text is close to useless when trying to re-analyze their results.

  3. Short versus Long Term
    As with other studies looking for long term detrimental effects, this study only required 2 weeks of abstinence and averaged only 4 weeks. Assessments of long term damage should be based on a minimum of 4 months of abstinence from use of the substance in question, or they run the risk of indicating (in this case) possible short term effects or medium term effects.

  4. Education differences
    This study allows for a 2 year average difference between the MDMA users and the non users, with the MDMA users having 2 years *less* than the controls.

  5. Statistics, Sampling, & Researcher Bias
    The subjects of this study were given a variety of tests and were subgroup separated in order to show increased differences between the MDMA versus non-MDMA subjects. 30 total MDMA users were tested, but only 25 users were included in the final analysis. In one particularly bizarre twist of interpretation they say:

    "As might be anticipated, when memory function in the two groups was compared without taking the average monthly MDMA dose into account, differences were not found."

    Which appears to be saying that there was no fundamental difference in memory scores between the MDMA and non MDMA using group. While a large variety of correlations were examined, including sex, age, vocabulary, dosage per month, total lifetime usage all crossed against every cognitive test they gave, the only correlations that implicated MDMA as a possible causal factor for the differences between the subjects scores were for low vocabulary MDMA users for the immediate verbal memory and delayed visual memory tests.

    They also acknowledge in the last paragraph of the paper that the data has "several potential limitations", but in their results and in the statements printed in major media, why does Ricaurte say things like: "Tests show that heavy Ecstasy users have damage to their visual and verbal memory," or Bolla: "Our study shows Ecstasy can be associated with memory damage".

    Conclusion:
    This study could provide a wealth of information, but instead the authors obscure the data behind over analysis. The study, by itself, says very little about the issue of memory impairment associated with MDMA use.