First-episode schizophrenia patients who used cannabis performed better on cognitive tests

First-episode schizophrenia patients with lifetime cannabis use (n=30) showed better cognitive performance than non-using patients (n=53), with the most prominent difference in visual memory. The two patient groups did not differ in symptom severity or medication. Among healthy controls, cannabis use made no cognitive difference.

Case-control study comparing cognitive test performance across four groups: first-episode schizophrenia patients who used cannabis (n=30), schizophrenia patients who did not (n=53), healthy controls who used cannabis (n=20), and healthy controls who did not (n=49). All underwent extensive neurocognitive assessment.

The finding that cannabis-using schizophrenia patients performed better cognitively challenges the assumption that cannabis worsens cognitive outcomes in psychosis. This pattern is consistent with the "dual pathway" hypothesis, where cannabis-related psychosis may require lower genetic vulnerability.

This finding does not mean cannabis protects cognition in schizophrenia. One leading interpretation is that people who develop psychosis through cannabis exposure may have needed less underlying genetic vulnerability, meaning they started from a higher cognitive baseline.

Small sample sizes. Cross-sectional design cannot determine causation. Lifetime cannabis use measured by questionnaire. Cannot distinguish between cannabis as cause vs. marker of different illness pathways.