Schizophrenia patients who used cannabis showed better brain processing than those who did not
Schizophrenia patients with cannabis use disorder showed greater mismatch negativity (MMN) amplitudes than schizophrenia patients without cannabis use, with levels comparable to healthy controls.
Quick Facts
What This Study Found
Schizophrenia patients without cannabis use showed reduced frontocentral MMN to duration deviants compared to healthy controls, as expected. However, schizophrenia patients with comorbid cannabis use showed greater MMN amplitudes than non-using patients, with no significant difference from healthy controls.
Key Numbers
20 schizophrenia patients without CUD, 21 with CUD, 20 healthy controls. Schizophrenia + CUD patients had greater MMN amplitudes than non-CUD patients at central electrodes.
How They Did This
Cross-sectional EEG study comparing 20 schizophrenia patients without CUD, 21 with CUD, and 20 healthy controls. Auditory oddball paradigm measured MMN to frequency and duration deviants.
Why This Research Matters
This counterintuitive finding suggests that schizophrenia patients who use cannabis may represent a cognitively less impaired subgroup, rather than cannabis protecting the brain. It challenges simple assumptions about cannabis always worsening cognition in psychosis.
The Bigger Picture
One interpretation is that cognitively better-functioning schizophrenia patients are more capable of obtaining and using cannabis. This would mean the association reflects patient characteristics rather than a cannabis benefit.
What This Study Doesn't Tell Us
Small cross-sectional study; cannot determine causation. The design cannot distinguish whether cannabis improved cognition or whether less impaired patients are more likely to use cannabis.
Questions This Raises
- ?Is this a selection effect (less impaired patients use more cannabis) or a cannabis effect (cannabis use preserves some cognitive function)?
- ?Would longitudinal studies clarify the direction of causation?
Trust & Context
- Key Stat:
- Cannabis-using schizophrenia patients had MMN comparable to healthy controls
- Evidence Grade:
- Preliminary: small cross-sectional EEG study with limited sample per group.
- Study Age:
- Published in 2019.
- Original Title:
- Impact of Chronic Cannabis Use on Auditory Mismatch Negativity Generation in Schizophrenia Patients.
- Published In:
- Pharmacopsychiatry, 52(3), 126-133 (2019)
- Authors:
- Roser, Patrik(9), Pichler, Eva-Maria(4), Habermeyer, Benedikt, Kawohl, Wolfram, Juckel, Georg
- Database ID:
- RTHC-02263
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What is mismatch negativity?
MMN is an automatic brain response when an unexpected sound occurs in a series of regular sounds. It reflects the brain's ability to detect changes and is typically reduced in schizophrenia, indicating impaired pre-attentive processing.
Does this mean cannabis helps cognition in schizophrenia?
Not necessarily. The authors suggest the more likely explanation is that less cognitively impaired patients are more likely to seek out and use cannabis, rather than cannabis improving their brain function.
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Cite This Study
https://rethinkthc.com/research/RTHC-02263APA
Roser, Patrik; Pichler, Eva-Maria; Habermeyer, Benedikt; Kawohl, Wolfram; Juckel, Georg. (2019). Impact of Chronic Cannabis Use on Auditory Mismatch Negativity Generation in Schizophrenia Patients.. Pharmacopsychiatry, 52(3), 126-133. https://doi.org/10.1055/a-0573-9866
MLA
Roser, Patrik, et al. "Impact of Chronic Cannabis Use on Auditory Mismatch Negativity Generation in Schizophrenia Patients.." Pharmacopsychiatry, 2019. https://doi.org/10.1055/a-0573-9866
RethinkTHC
RethinkTHC Research Database. "Impact of Chronic Cannabis Use on Auditory Mismatch Negativi..." RTHC-02263. Retrieved from https://rethinkthc.com/research/roser-2019-impact-of-chronic-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.