Among 104 first-episode psychosis patients, cannabis users showed better attention and executive function than non-users at baseline and after one year, suggesting they may represent a cognitively higher-functioning subgroup.
Read this if you want to understand the complex relationship between cannabis use and cognitive function in people with psychosis.
Cannabis-using psychosis patients had better attention and executive function
What the researchers found
Researchers compared cognitive functioning between cannabis-using and non-using patients with first-episode schizophrenia. The results contradicted expectations.
Cannabis-using patients (47 users) performed better on attention and executive function tests than non-users (57 non-users) both at initial assessment and after one year of treatment. Both groups improved similarly over the follow-up period.
Cannabis users also had better social premorbid adjustment, particularly during early life stages. The amount of cannabis consumed and duration of use did not correlate with cognitive performance.
The authors concluded that cannabis-using schizophrenia patients may represent a distinct subgroup with better baseline cognitive abilities and social functioning prior to illness onset.
Why it matters
The finding challenged the assumption that cannabis always worsens cognitive outcomes in schizophrenia, suggesting instead that cannabis-using patients may have had better functioning to begin with.
The numbers in context
104 patients (47 cannabis users, 57 non-users) and 37 healthy controls. Cannabis users performed better on attention and executive function at baseline and 1-year follow-up. Amount and duration of cannabis use did not predict cognitive performance.
How the study worked
Longitudinal study of 104 first-episode non-affective psychosis patients (47 cannabis users, 57 non-users) and 37 healthy controls. Cross-sectional and one-year longitudinal cognitive assessments with clinical and premorbid adjustment measures.
What this study cannot tell us
Observational design cannot determine causation. Better cognition in users may reflect selection effects (higher-functioning people being more socially engaged and thus more exposed to cannabis). Cannabis use was assessed prior to illness onset only.
How to read the evidence
Longitudinal study with one-year follow-up and healthy control group, but observational design limits causal conclusions.
When this study was published
Published in 2010. The "paradox" of better cognition in cannabis-using psychosis patients has continued to be studied.
The bigger picture
This study contributed to a growing body of research suggesting that the relationship between cannabis and psychosis is more complex than simple harm, with cannabis-using patients potentially representing a distinct clinical subgroup.
Questions still open
- Do people with better cognitive function seek out cannabis more, or does cannabis use select for a different pathway to psychosis? How should treatment differ for these subgroups?
Common questions
Does cannabis improve cognition in people with schizophrenia?
Why would cannabis users have better cognitive function?
Read the original research
Cannabis use and cognitive functioning in first-episode schizophrenia patients.
Schizophrenia research, 124(1-3), 142-51
Citation
Rodríguez-Sánchez, José Manuel; Ayesa-Arriola, Rosa; Mata, Ignacio; Moreno-Calle, Teresa; Perez-Iglesias, Rocío; González-Blanch, César; Periañez, José Antonio; Vazquez-Barquero, José Luis; Crespo-Facorro, Benedicto. (2010). Cannabis use and cognitive functioning in first-episode schizophrenia patients.. Schizophrenia research, 124(1-3), 142-51. https://doi.org/10.1016/j.schres.2010.08.017
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