In a pilot fMRI study, schizophrenia patients showed abnormal default mode network hyperconnectivity at baseline, but cannabinoid administration reduced this hyperconnectivity and improved the brain network patterns associated with working memory.
Schizophrenia researchers, neuroimaging scientists, dual-diagnosis clinicians.
Cannabinoid administration reduced default mode network hyperconnectivity in schizophrenia patients and improved the brain pattern associated with working memory.
What the researchers found
At baseline, schizophrenia patients showed DMN hyperconnectivity (correlated with positive symptom severity) and reduced anticorrelation between the DMN and executive control network compared to controls. After cannabinoid administration, DMN hyperconnectivity was reduced and DMN-ECN anticorrelation increased. The magnitude of anticorrelation after cannabinoid administration correlated with working memory performance.
Why it matters
DMN hyperconnectivity is a consistent finding in schizophrenia and is linked to psychotic symptoms. The remarkable finding that cannabinoids normalized this aberrant connectivity suggests a potential mechanism by which some schizophrenia patients may derive benefit from cannabis use, despite its general risks.
The numbers in context
12 patients, 12 controls. DMN hyperconnectivity at baseline correlated with positive symptom severity. After cannabinoid administration, DMN connectivity normalized toward control levels. Post-cannabinoid DMN-ECN anticorrelation correlated with working memory performance.
How the study worked
Pilot study with 12 schizophrenia-CUD patients and 12 healthy controls. Resting-state fMRI at baseline and after patients smoked a 3.6% THC cannabis cigarette or ingested a 15 mg THC pill. Default mode network connectivity analyzed.
What this study cannot tell us
Very small pilot (n=12 per group). No placebo control for the cannabinoid administration. Low THC dose (3.6% or 15 mg). Cannot determine whether this network normalization translates to clinical benefit. Acute effects may differ from chronic effects.
How to read the evidence
Preliminary - very small pilot without placebo control, but novel and clinically provocative finding.
When this study was published
Published in 2018.
The bigger picture
This pilot challenges the simple narrative that cannabis is uniformly harmful in psychosis. The finding that cannabinoids normalized a key brain network abnormality suggests the relationship between cannabis and psychosis is more complex than currently understood.
Questions still open
- Could cannabinoids be therapeutically useful for normalizing DMN connectivity in schizophrenia? Is this effect specific to THC, or would CBD produce similar network changes? Does this explain why some schizophrenia patients report benefits from cannabis?
Common questions
Can cannabis improve brain function in schizophrenia?
What is the default mode network?
Read the original research
Understanding marijuana's effects on functional connectivity of the default mode network in patients with schizophrenia and co-occurring cannabis use disorder: A pilot investigation.
Schizophrenia research, 194, 70-77
Citation
Whitfield-Gabrieli, Susan; Fischer, Adina S; Henricks, Angela M; Khokhar, Jibran Y; Roth, Robert M; Brunette, Mary F; Green, Alan I. (2018). Understanding marijuana's effects on functional connectivity of the default mode network in patients with schizophrenia and co-occurring cannabis use disorder: A pilot investigation.. Schizophrenia research, 194, 70-77. https://doi.org/10.1016/j.schres.2017.07.029
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