Large genetic study identified shared DNA between smoking, cannabis use, and schizophrenia
A genome-wide analysis of over 780,000 people found a shared genetic factor explaining 8.6% of schizophrenia risk, with the gene NCAM1 emerging as a key link between smoking, cannabis use, and schizophrenia.
Quick Facts
What This Study Found
A common genetic factor of cannabis and cigarette smoking explained 8.6% of schizophrenia heritability. Twenty independent loci were identified, with NCAM1 (neural cell adhesion molecule 1) highlighted as a top risk gene. Risk genes were enriched in cortex, neurons, and dendritic spines.
Key Numbers
Over 780,000 total participants. Shared genetic factor explained 8.6% of schizophrenia heritability. 20 independent genome-wide significant loci. Top variant rs7945073 on chromosome 11. Genetic correlations with ADHD (r=0.50), social deprivation (r=0.58), lifestyle problems (r=0.83).
How They Did This
Leveraged genome-wide summary statistics from three large datasets: schizophrenia (n=99,934), cigarette smoking (n=518,633), and cannabis usage (n=162,082). Applied CAUSE and Genomic SEM to identify shared genetic architecture.
Why This Research Matters
This study provides genetic evidence that the association between cannabis/smoking and schizophrenia is partly driven by shared biology, not just behavioral choices. NCAM1 is involved in neurodevelopment, suggesting a common vulnerability.
The Bigger Picture
The debate over whether cannabis causes schizophrenia or whether shared genetics explain both is central to public health policy. This study supports the shared genetics model while not ruling out direct causal effects.
What This Study Doesn't Tell Us
Summary-level statistics cannot establish individual-level causation. The study population was primarily European ancestry. The 8.6% explained heritability leaves most of the shared risk unexplained.
Questions This Raises
- ?Does the shared genetic factor mean cannabis is less causally related to schizophrenia than assumed?
- ?Could NCAM1 variants identify individuals at highest risk?
- ?Do the remaining 91.4% of schizophrenia heritability factors interact with cannabis use?
Trust & Context
- Key Stat:
- Shared genetic factor explained 8.6% of schizophrenia heritability
- Evidence Grade:
- Strong: very large combined sample (780,000+), rigorous genomic methods, multiple validation approaches.
- Study Age:
- Published in 2022.
- Original Title:
- Genome-wide identification of the shared genetic basis of cannabis and cigarette smoking and schizophrenia implicates NCAM1 and neuronal abnormality.
- Published In:
- Psychiatry research, 310, 114453 (2022)
- Authors:
- Song, Weichen, Lin, Guan Ning, Yu, Shunying, Zhao, Min
- Database ID:
- RTHC-04239
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
What is NCAM1?
NCAM1 (neural cell adhesion molecule 1) is a gene involved in brain development, specifically in how neurons connect and communicate. It was identified as the top risk gene shared between smoking, cannabis use, and schizophrenia.
Does this mean cannabis does not cause schizophrenia?
Not exactly. It means some of the association is explained by shared genetics, so people genetically predisposed to schizophrenia may also be predisposed to use cannabis. But this does not rule out that cannabis also has direct effects on psychosis risk.
What else was genetically correlated?
The shared genetic factor was also correlated with ADHD risk (r=0.50), social deprivation (r=0.58), lifestyle problems (r=0.83), and pregnancy loss (r=0.60).
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Cite This Study
https://rethinkthc.com/research/RTHC-04239APA
Song, Weichen; Lin, Guan Ning; Yu, Shunying; Zhao, Min. (2022). Genome-wide identification of the shared genetic basis of cannabis and cigarette smoking and schizophrenia implicates NCAM1 and neuronal abnormality.. Psychiatry research, 310, 114453. https://doi.org/10.1016/j.psychres.2022.114453
MLA
Song, Weichen, et al. "Genome-wide identification of the shared genetic basis of cannabis and cigarette smoking and schizophrenia implicates NCAM1 and neuronal abnormality.." Psychiatry research, 2022. https://doi.org/10.1016/j.psychres.2022.114453
RethinkTHC
RethinkTHC Research Database. "Genome-wide identification of the shared genetic basis of ca..." RTHC-04239. Retrieved from https://rethinkthc.com/research/song-2022-genomewide-identification-of-the
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.