Ecstasy Users Showed Cognitive Decline While Cannabis-Only Users Did Not Differ From Non-Users | Research

The takeaway

In a three-group comparison, ecstasy users who also used cannabis showed impaired attention, memory, and intelligence measures, while cannabis-only users performed no differently from drug-free controls.

Read this if you want to understand which drug, ecstasy or cannabis, is more likely responsible for cognitive problems in polydrug users.

Cannabis-only users showed no cognitive differences from non-users

What the researchers found

Researchers compared cognitive performance across three carefully matched groups of 28 participants each: ecstasy users (who also used cannabis), cannabis-only users, and non-users. The ecstasy users had typical recreational use patterns, not extremely heavy use.

Ecstasy users performed normally on simple attention tests but showed significant impairment on complex attention tasks, memory and learning, and aspects of general intelligence. Heavier ecstasy and cannabis use correlated with poorer performance within the ecstasy group.

The cannabis-only group did not differ significantly from non-users on any cognitive measure.

The researchers attributed the cognitive decline primarily to ecstasy's known neurotoxic effects on the serotonin system, suggesting that even typical recreational doses may cause sufficient neurotoxicity to impair cognition in otherwise healthy young people. A working memory impairment was proposed as the common denominator.

Why it matters

By including a cannabis-only comparison group, this study could separate ecstasy effects from cannabis effects. The finding that cannabis-only users showed no cognitive impairment relative to non-users (while ecstasy users did) suggested that cannabis was not the driver of cognitive problems in polydrug-using populations.

The numbers in context

Three groups of 28. Ecstasy users impaired on complex attention, memory, and intelligence. Cannabis users not different from non-users. Heavier ecstasy and cannabis use correlated with worse performance in ecstasy group only.

How the study worked

Cross-sectional comparison of three matched groups of 28: abstinent ecstasy+cannabis users, cannabis-only users, and non-users. Comprehensive cognitive battery assessing attention, memory, learning, and intelligence. All participants were drug-free at testing.

What this study cannot tell us

Small sample (28 per group). Cross-sectional design. The ecstasy group used cannabis concurrently, so additive or interactive effects cannot be fully separated. Self-reported drug histories. "Cannabis-only" may still include unreported other drug use.

How to read the evidence

A well-designed three-group comparison with matched controls and comprehensive testing. Limited by small sample size and cross-sectional design.

When this study was published

Published in 2000. Subsequent research has continued to explore whether cannabis use modifies ecstasy's neurotoxic effects.

The bigger picture

This study demonstrated the importance of separating cannabis effects from effects of other commonly co-used drugs. Many studies attributing cognitive deficits to cannabis fail to control for ecstasy, stimulant, or other drug use.

Questions still open

Are the cognitive deficits in ecstasy users driven by ecstasy, cannabis, or their interaction? Would longer-term cannabis-only users show deficits not seen in this sample? Does cannabis modulate ecstasy's neurotoxicity?

Common questions

Does cannabis cause cognitive problems?

In this study, cannabis-only users showed no cognitive differences from non-users. The cognitive impairments seen in the ecstasy group were attributed to ecstasy's neurotoxic effects, not cannabis.

Does ecstasy affect cognition?

Yes. Even at typical recreational doses, ecstasy users showed impaired complex attention, memory, and aspects of intelligence compared to both cannabis-only users and non-users.

Read the original research

Impaired cognitive performance in drug free users of recreational ecstasy (MDMA).

Journal of neurology, neurosurgery, and psychiatry, 68(6), 719-25

View on PubMed ↗

Citation

Gouzoulis-Mayfrank, E; Daumann, J; Tuchtenhagen, F; Pelz, S; Becker, S; Kunert, H J; Fimm, B; Sass, H. (2000). Impaired cognitive performance in drug free users of recreational ecstasy (MDMA).. Journal of neurology, neurosurgery, and psychiatry, 68(6), 719-25.