In a three-group comparison, both cannabis and ecstasy users showed verbal memory impairment, but only ecstasy users had additional delayed memory deficits, and neither group recognized their own cognitive problems.
Read this if you use cannabis or ecstasy and want to understand how these substances affect different types of memory.
Users were not aware of their own cognitive deficits despite objective impairment
What the researchers found
Researchers compared cognitive function across three groups of 15 young people: regular ecstasy users, regular cannabis users who had never taken ecstasy, and drug-free controls.
Reaction times (visual, auditory, complex) were similar across all three groups. Visual memory, attention, and concentration also showed no differences.
Verbal memory was impaired in both cannabis users and ecstasy users compared to controls. However, delayed memory (the ability to recall information after a time gap) was impaired only in ecstasy users, distinguishing their cognitive profile from cannabis users.
A notable secondary finding: despite objective cognitive impairments, neither user group reported more cognitive failures in daily life than controls on the Cognitive Failures Questionnaire. Users were not aware of their own deficits.
Why it matters
Unlike the previous ecstasy-cannabis comparison (RTHC-00093) which found no cannabis effects, this study found verbal memory impairment in both groups. The discrepancy highlights how study design, tests used, and population characteristics affect findings. The lack of self-awareness of deficits is clinically important.
The numbers in context
Three groups of 15. Verbal memory impaired in both user groups. Delayed memory impaired only in ecstasy users. Reaction times unaffected in all groups. No subjective awareness of cognitive deficits.
How the study worked
Cross-sectional comparison of three groups of 15: ecstasy users, cannabis-only users, and non-users. Wechsler Memory Scale (revised) and computerized reaction time tasks administered while drug-free. Cognitive Failures Questionnaire assessed subjective cognitive complaints.
What this study cannot tell us
Very small groups (15 each). Cannabis users varied in frequency and duration of use. Self-reported drug history without verification. Cross-sectional design cannot determine causation. The ecstasy group may have differed from cannabis group in other unmeasured ways.
How to read the evidence
A three-group comparison with standardized cognitive testing. Useful design but very small groups (N=15 each) limit statistical power.
When this study was published
Published in 2000. Research on cannabis and memory has expanded substantially with larger samples and more sophisticated testing.
The bigger picture
The finding that users did not recognize their own cognitive impairments has practical implications: cannabis and ecstasy users may not seek help for cognitive problems because they do not perceive them, and they may engage in complex tasks (driving, studying) while objectively impaired but subjectively unaware.
Questions still open
- Why did this study find cannabis-related verbal memory effects while the earlier study (RTHC-00093) did not? Does the lack of self-awareness worsen over time? Would the verbal memory deficit reverse with abstinence?
Common questions
Does cannabis affect memory?
How does cannabis compare to ecstasy for memory?
Read the original research
Cognitive performance amongst recreational users of "ecstasy".
Psychopharmacology, 151(1), 19-24
Citation
Rodgers, J. (2000). Cognitive performance amongst recreational users of "ecstasy".. Psychopharmacology, 151(1), 19-24.
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