Schizophrenia Patients Who Used Cannabis Had Better Emotional Memory and More Normal Brain Activity | Research

The takeaway

Schizophrenia patients with a history of cannabis abuse showed better emotional memory and more preserved prefrontal brain function compared to non-using schizophrenia patients, though they still performed below healthy controls.

Read this if you are interested in why some people with schizophrenia continue to use cannabis despite medical advice.

Cannabis-using patients preserved frontal lobe function that non-users lost

What the researchers found

Researchers compared emotional memory and brain activation in three groups: 14 schizophrenia patients with cannabis abuse (dual-diagnosis, DD), 14 non-using schizophrenia patients (SCZ), and 21 healthy controls (HC). Non-using schizophrenia patients showed prominent impairment in recognizing both positive and negative emotional images, while cannabis-using patients showed smaller differences from healthy controls.

Brain imaging revealed that non-using patients activated different brain regions (temporal, parietal, limbic, occipital) while cannabis-using patients showed activation patterns more similar to controls, particularly preserving frontal and limbic region activity.

Why it matters

Emotional memory is critical for social functioning and quality of life. The finding that cannabis-using patients have relatively preserved emotional memory and prefrontal function may help explain why some patients use cannabis, potentially to maintain emotional and cognitive abilities that are otherwise impaired by their illness.

The numbers in context

14 DD patients, 14 SCZ patients, 21 healthy controls. Non-users showed prominent impairment for both positive and negative emotional recognition. Cannabis users showed smaller differences from controls. Cannabis users preserved frontal and limbic activation patterns.

How the study worked

Cross-sectional fMRI study comparing three groups during an emotional memory recognition task with positive and negative pictures. 14 dual-diagnosis patients, 14 non-using schizophrenia patients, 21 healthy controls.

What this study cannot tell us

Small sample sizes (14 per patient group) limit generalizability. Cross-sectional design cannot determine whether better function preceded cannabis use or resulted from it. Cannabis abuse has other negative consequences (poor compliance, relapse) that this study did not address. The groups may differ on unmeasured variables.

How to read the evidence

Small cross-sectional fMRI study; preliminary evidence that adds to the "cognitively less impaired" hypothesis.

When this study was published

Published in 2013. The relationship between cannabis use and cognitive function in schizophrenia continues to be investigated.

The bigger picture

This study adds to the growing evidence that cannabis-using schizophrenia patients may represent a cognitively less impaired subgroup. Their relatively preserved emotional memory could be a reason they seek cannabis, or it could reflect a different underlying neurobiology that both enables cannabis seeking and confers cognitive resilience.

Questions still open

Does cannabis use actively preserve emotional memory in schizophrenia, or are patients with better function simply more likely to use cannabis? Would these patients do even better without cannabis? Does the preserved emotional function translate to better social outcomes?

Common questions

Why would cannabis-using schizophrenia patients have better memory?

The leading explanation is not that cannabis improves memory, but that patients who develop schizophrenia with cannabis exposure may have started with better cognitive function. They may have needed the additional risk from cannabis to develop psychosis, whereas patients without cannabis exposure developed it from internal vulnerability alone, which is associated with greater cognitive impairment.

Should schizophrenia patients use cannabis to improve their cognition?

No. Despite the cognitive advantages found in cannabis-using patients, cannabis abuse in schizophrenia is associated with poor medication compliance, more frequent psychotic relapses, and worse overall outcomes. The cognitive differences likely reflect pre-existing differences between patient subgroups rather than a beneficial effect of cannabis.

Read the original research

Cannabis abuse is associated with better emotional memory in schizophrenia: a functional magnetic resonance imaging study.

Psychiatry research, 214(1), 24-32

View on PubMed ↗Publisher’s paper ↗

Citation

Bourque, Josiane; Mendrek, Adrianna; Durand, Myriam; Lakis, Nadia; Lipp, Olivier; Stip, Emmanuel; Lalonde, Pierre; Grignon, Sylvain; Potvin, Stéphane. (2013). Cannabis abuse is associated with better emotional memory in schizophrenia: a functional magnetic resonance imaging study.. Psychiatry research, 214(1), 24-32. https://doi.org/10.1016/j.pscychresns.2013.05.012