None of 10 Previously Reported Cannabis Genes Replicated in a Large Twin Study
A study of 7,452 twins tested 10 candidate genes previously linked to cannabis use and found that none reached even nominal statistical significance, suggesting earlier findings may have been false positives.
Quick Facts
What This Study Found
Researchers used a large Australian twin family sample to test whether 10 genes previously reported to be associated with cannabis use actually replicated. Using a gene-based association test (which is more powerful than single-variant tests), none of the candidate genes reached even the most lenient significance threshold (p<0.05).
The authors concluded that the failure to replicate likely reflects limited understanding of cannabis neurobiology, potential publication bias in earlier studies, and the likelihood of false-positive findings in the original reports.
Key Numbers
7,452 participants. 10 candidate genes tested. None reached p<0.05. This is consistent with the broader "replication crisis" in candidate gene studies for behavioral traits.
How They Did This
Gene-based association testing in 7,452 participants from an Australian twin family sample. Tested 10 candidate genes previously reported as associated with lifetime frequency of cannabis use. The gene-based approach aggregates signal across all variants within each gene, providing more power than single-SNP tests.
Why This Research Matters
While cannabis use is clearly heritable (twin studies show this consistently), identifying the specific genes involved has proven extremely difficult. This large non-replication study serves as a cautionary example about the reliability of candidate gene findings in psychiatric genetics.
The Bigger Picture
This study appeared at a pivotal moment in psychiatric genetics, as the field was shifting from small candidate gene studies to large genome-wide association studies (GWAS). The failure of all 10 candidates to replicate in a well-powered sample illustrated why this shift was necessary.
What This Study Doesn't Tell Us
The study tested lifetime frequency of cannabis use, not cannabis dependence, which may have different genetic architecture. The Australian sample may differ genetically from the populations in which the original associations were found. Gene-based tests, while more powerful for some signals, may miss specific variants.
Questions This Raises
- ?Which, if any, specific genes genuinely influence cannabis use?
- ?Will genome-wide approaches succeed where candidate gene studies have failed?
- ?How much of cannabis use heritability can eventually be explained by identified genetic variants?
Trust & Context
- Key Stat:
- 0 of 10 candidate genes replicated at even p<0.05
- Evidence Grade:
- Well-powered replication study in a large twin sample; provides strong evidence against the tested candidate genes.
- Study Age:
- Published in 2012. Genome-wide association studies have since identified some genetic variants associated with cannabis use, though effect sizes are very small.
- Original Title:
- No association of candidate genes with cannabis use in a large sample of Australian twin families.
- Published In:
- Addiction biology, 17(3), 687-90 (2012)
- Authors:
- Verweij, Karin J H(8), Zietsch, Brendan P(2), Liu, Jimmy Z, Medland, Sarah E, Lynskey, Michael T, Madden, Pamela A F, Agrawal, Arpana, Montgomery, Grant W, Heath, Andrew C, Martin, Nicholas G
- Database ID:
- RTHC-00631
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Is cannabis use genetic?
Twin studies consistently show that cannabis use is heritable, with genetics explaining roughly 40-60% of the variation. However, identifying the specific genes responsible has proven very difficult. This study found that 10 genes previously claimed to be involved did not replicate, suggesting the earlier findings were false leads.
Why do genetic findings for cannabis use fail to replicate?
Several factors contribute: the original studies were often too small, leading to statistical flukes being mistaken for real findings. Publication bias means positive results get published while failed replications do not. And cannabis use is likely influenced by many genes, each with tiny effects, making individual gene identification extremely challenging.
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Cite This Study
https://rethinkthc.com/research/RTHC-00631APA
Verweij, Karin J H; Zietsch, Brendan P; Liu, Jimmy Z; Medland, Sarah E; Lynskey, Michael T; Madden, Pamela A F; Agrawal, Arpana; Montgomery, Grant W; Heath, Andrew C; Martin, Nicholas G. (2012). No association of candidate genes with cannabis use in a large sample of Australian twin families.. Addiction biology, 17(3), 687-90. https://doi.org/10.1111/j.1369-1600.2011.00320.x
MLA
Verweij, Karin J H, et al. "No association of candidate genes with cannabis use in a large sample of Australian twin families.." Addiction biology, 2012. https://doi.org/10.1111/j.1369-1600.2011.00320.x
RethinkTHC
RethinkTHC Research Database. "No association of candidate genes with cannabis use in a lar..." RTHC-00631. Retrieved from https://rethinkthc.com/research/verweij-2012-no-association-of-candidate
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.