Schizophrenia patients showed reduced gray matter compared to healthy controls, but having a history of cannabis or alcohol use did not make those brain differences any worse.
Researchers studying schizophrenia, clinicians working with dual-diagnosis patients.
92 schizophrenia patients with substance use and 66 without showed identical patterns of gray matter reduction.
What the researchers found
Using voxel-based morphometry, researchers found that schizophrenia patients had reduced gray matter in several brain regions regardless of substance use history. No additional gray matter differences were found between patients with and without cannabis/alcohol use histories.
Why it matters
A major concern in schizophrenia research is whether substance use confounds brain structure findings. This study suggests that cannabis and alcohol use do not significantly worsen the gray matter reductions already associated with schizophrenia.
The numbers in context
158 schizophrenia patients total (92 with and 66 without substance use history) compared to 88 healthy controls. Gray matter reductions were found in bilateral precentral gyrus, right medial frontal cortex, right thalamus, bilateral amygdala, and bilateral cerebellum.
How the study worked
VBM brain imaging compared 92 schizophrenia patients with substance use histories, 66 without substance use histories, and 88 healthy controls.
What this study cannot tell us
Cross-sectional design limits causal conclusions. Substance use histories were clinically assessed rather than biologically verified. The study did not examine other brain measures like white matter or functional connectivity.
How to read the evidence
Moderate - adequate sample size and well-established methodology, but cross-sectional design.
When this study was published
Published in 2018.
The bigger picture
This finding helps clarify the relationship between substance use and brain changes in schizophrenia. While substances may affect the brain in other ways, they do not appear to compound the specific gray matter deficits characteristic of the disorder.
Questions still open
- Could substance use affect brain function without changing gray matter volume? Do different types or amounts of substance use produce different effects? What about other substances beyond cannabis and alcohol?
Common questions
Does cannabis make brain damage worse in schizophrenia?
Can substance use confound brain studies in schizophrenia?
Read the original research
Impact of substance use disorder on gray matter volume in schizophrenia.
Psychiatry research. Neuroimaging, 280, 9-14
Citation
Quinn, Margaret; McHugo, Maureen; Armstrong, Kristan; Woodward, Neil; Blackford, Jennifer; Heckers, Stephan. (2018). Impact of substance use disorder on gray matter volume in schizophrenia.. Psychiatry research. Neuroimaging, 280, 9-14. https://doi.org/10.1016/j.pscychresns.2018.08.002
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