Cannabis use did not worsen cognition in first-episode schizophrenia, but methamphetamine did
Over two years of treatment, methamphetamine use predicted less cognitive improvement in schizophrenia patients, while cannabis use did not.
Quick Facts
What This Study Found
In 81 patients with first-episode schizophrenia spectrum disorders treated over 24 months, positive methamphetamine tests predicted less cognitive improvement, but positive cannabis tests did not.
Key Numbers
81 patients and 100 controls followed for 24 months. Patients improved cognitively with treatment but remained significantly below controls throughout. Methamphetamine, not cannabis, predicted less cognitive improvement.
How They Did This
Longitudinal cohort study of 81 patients treated with flupenthixol decanoate over 24 months. Cognition assessed with the MATRICS battery at four time points; urine testing for cannabis and methamphetamine at six time points. Compared to 100 matched controls.
Why This Research Matters
This study helps disentangle the cognitive effects of different substances in people with schizophrenia, a population where substance use is common and cognitive outcomes are critical for functioning.
The Bigger Picture
While both cannabis and methamphetamine are commonly used by people with psychotic disorders, their cognitive effects appear to differ substantially. This distinction matters for clinical decision-making.
What This Study Doesn't Tell Us
Substance use was measured by urine testing, which has a limited detection window. The study was observational, so it cannot establish causation. Sample size was moderate.
Questions This Raises
- ?Does cannabis truly have no cognitive impact in schizophrenia, or is the effect too small for this sample to detect?
- ?Would results differ with heavier cannabis use?
- ?Does cannabis type or potency matter?
Trust & Context
- Key Stat:
- Cannabis use did not predict cognitive decline over 24 months
- Evidence Grade:
- Moderate: longitudinal design with standardized assessments and matched controls, but observational with moderate sample size.
- Study Age:
- Published in 2022.
- Original Title:
- The associations of cannabis and methamphetamine use with cognitive performance over the first 2 years of treatment in schizophrenia spectrum disorders.
- Published In:
- Early intervention in psychiatry, 16(11), 1230-1239 (2022)
- Authors:
- Scheffler, Freda(3), Phahladira, Lebogang(2), Hendrikse, Chanellé B, du Plessis, Stefan, Asmal, Laila, Luckhoff, Hilmar K, Smit, Anna Margaretha, Olivier, M Riaan, Emsley, Robin
- Database ID:
- RTHC-04198
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Did patients with schizophrenia improve cognitively over time?
Yes, patients showed cognitive improvement with treatment, but their scores remained significantly below those of healthy controls at all time points.
Why might methamphetamine affect cognition differently than cannabis?
Methamphetamine is a potent dopamine-releasing agent with well-documented neurotoxic effects, while cannabis acts through the endocannabinoid system. Their distinct pharmacological profiles may explain the different cognitive impacts.
Does this mean cannabis is safe for people with schizophrenia?
This study only examined cognitive effects. Cannabis use is associated with other risks in psychotic disorders, including symptom worsening and relapse.
Read More on RethinkTHC
- THC-amygdala-anxiety-brain
- anandamide-weed-withdrawal
- cannabinoid-receptors-recovery-time
- cannabis-developing-brain-teenagers
- cant-enjoy-anything-without-weed
- dopamine-recovery-after-quitting-weed
- endocannabinoid-system-explained-simply
- endocannabinoid-system-withdrawal
- nervous-system-weed-withdrawal-fight-flight
- teen-weed-use-under-18-effects-brain
- thc-brain-withdrawal
- thc-prefrontal-cortex-brain-effects
- weed-cortisol-stress-hormones
- weed-memory-loss-recovery
- weed-motivation-amotivational-syndrome
- weed-nervous-system-effects
- weed-reward-system-brain
Cite This Study
https://rethinkthc.com/research/RTHC-04198APA
Scheffler, Freda; Phahladira, Lebogang; Hendrikse, Chanellé B; du Plessis, Stefan; Asmal, Laila; Luckhoff, Hilmar K; Smit, Anna Margaretha; Olivier, M Riaan; Emsley, Robin. (2022). The associations of cannabis and methamphetamine use with cognitive performance over the first 2 years of treatment in schizophrenia spectrum disorders.. Early intervention in psychiatry, 16(11), 1230-1239. https://doi.org/10.1111/eip.13272
MLA
Scheffler, Freda, et al. "The associations of cannabis and methamphetamine use with cognitive performance over the first 2 years of treatment in schizophrenia spectrum disorders.." Early intervention in psychiatry, 2022. https://doi.org/10.1111/eip.13272
RethinkTHC
RethinkTHC Research Database. "The associations of cannabis and methamphetamine use with co..." RTHC-04198. Retrieved from https://rethinkthc.com/research/scheffler-2022-the-associations-of-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.