Schizophrenia patients with cannabis history showed better cognitive performance and more brain activity than non-users | Research

The takeaway

In an fMRI study, first-episode schizophrenia patients with a cannabis history performed better on cognitive control tasks and showed higher prefrontal cortex activation than patients without cannabis history, though both groups performed worse than healthy controls.

Psychiatrists, neuroimaging researchers, and psychosis-cannabis researchers

48 cannabis-using vs 28 non-using schizophrenia patients compared by fMRI

What the researchers found

First-episode schizophrenia patients with cannabis history (FES+CAN, n=48) showed higher cognitive control performance and higher dorsolateral prefrontal cortex (DLPFC) activation during task-based fMRI compared to patients without cannabis history (FES-CAN, n=28). FES+CAN and healthy controls (n=59) had similar DLPFC activation levels. However, younger cannabis initiation age was associated with lower IQ and functioning.

Why it matters

The paradox of better cognitive function in cannabis-using schizophrenia patients has been replicated across studies. This fMRI evidence adds a neural basis, suggesting these patients may have better-preserved prefrontal function.

The numbers in context

48 FES+CAN; 28 FES-CAN; 59 controls; FES+CAN showed higher cognitive control (d-context) than FES-CAN (p < .05); FES+CAN and CON had similar DLPFC activation; earlier cannabis onset linked to lower IQ; more frequent use linked to higher reality distortion

How the study worked

Cross-sectional fMRI study of 48 first-episode schizophrenia patients with cannabis history, 28 without, and 59 healthy controls performing the AX-Continuous Performance Task measuring cognitive control.

What this study cannot tell us

Cross-sectional design cannot determine causality or direction of association; selection bias (better-functioning patients may be more likely to access and use cannabis); cannot assess premorbid cognitive function; cannabis history based on self-report; relatively small groups

How to read the evidence

Well-designed neuroimaging study with appropriate controls, but cross-sectional design cannot resolve the selection vs. causation question.

When this study was published

2024 study

The bigger picture

One explanation is that cannabis use in schizophrenia may select for individuals with better premorbid cognitive functioning. This does not mean cannabis is protective, as earlier initiation and heavier use still predicted worse outcomes.

Questions still open

Does cannabis use in schizophrenia reflect a selection effect (higher-functioning patients use cannabis) or does cannabis exposure somehow preserve prefrontal function? Would longitudinal data clarify this paradox?

Common questions

Why do schizophrenia patients who use cannabis perform better cognitively?

This is a well-replicated paradox. One likely explanation is selection bias: individuals with better premorbid cognitive functioning and brain health may be more likely to seek out and obtain cannabis. The fMRI data showed their prefrontal cortex was more active during cognitive tasks, similar to healthy controls.

Does this mean cannabis helps schizophrenia?

No. While cannabis-using patients showed better cognitive performance, younger cannabis initiation age was associated with lower IQ and worse global functioning, and more frequent use correlated with more psychotic symptoms. The cognitive advantage likely reflects who uses cannabis rather than a benefit of cannabis itself.

Read the original research

Using Task-fMRI to Explore the Relationship Between Lifetime Cannabis Use and Cognitive Control in Individuals With First-Episode Schizophrenia.

Schizophrenia bulletin open, 5(1), sgae016

View on PubMed ↗Publisher’s paper ↗

Citation

Lesh, Tyler A; Rhilinger, Joshua; Brower, Rylee; Mawla, Alex M; Ragland, J Daniel; Niendam, Tara A; Carter, Cameron S. (2024). Using Task-fMRI to Explore the Relationship Between Lifetime Cannabis Use and Cognitive Control in Individuals With First-Episode Schizophrenia.. Schizophrenia bulletin open, 5(1), sgae016. https://doi.org/10.1093/schizbullopen/sgae016