Cannabis initiation was 44% heritable in the Netherlands, similar to countries with stricter laws
A Dutch twin study of 3,115 twins found 44% genetic influence on cannabis initiation, with 31% shared environment and 24% unique environment, similar to findings from countries where cannabis is illegal.
Quick Facts
What This Study Found
Researchers examined cannabis initiation in 3,115 Dutch twins with a mean age of 27.4 years. The Netherlands permits small-scale cannabis use, providing a natural experiment to test whether liberal drug policy changes the genetic-environmental balance.
Genetic influences accounted for 44% of individual differences in cannabis initiation. Shared environmental factors (family, peers, neighborhood) explained 31%, and unique environmental factors explained 24%.
These proportions were remarkably similar to those found in the United States, Australia, and United Kingdom, where cannabis policies were more restrictive. The authors concluded that the relative importance of genetic and environmental factors was not meaningfully different in a country with more liberal cannabis policy.
Key Numbers
3,115 twins, mean age 27.4 (SD 4.7). Heritability: 44%. Shared environment: 31%. Unique environment: 24%. Results comparable to US, Australia, and UK estimates.
How They Did This
Twin study of 3,115 twins (mean age 27.4) from the Netherlands Twin Register. Standard genetic modeling to estimate additive genetic (A), shared environmental (C), and unique environmental (E) contributions to cannabis initiation.
Why This Research Matters
The finding that heritability proportions were similar regardless of legal context suggested that genetic vulnerability to cannabis use operates independent of policy environment.
The Bigger Picture
This cross-national comparison suggested that while drug policy affects overall prevalence, the relative balance between genetic and environmental influences on who within a population tries cannabis remains stable across different policy environments.
What This Study Doesn't Tell Us
Single-country study with self-reported cannabis use. The Netherlands policy specifically applies to small amounts; results might differ under full legalization. Twin studies assume equal environments for identical and fraternal twins.
Questions This Raises
- ?Would full legalization with commercial sales change the heritability balance?
- ?Does permissive policy mainly increase overall rates while leaving genetic vulnerability unchanged?
Trust & Context
- Key Stat:
- 44% heritability regardless of liberal Dutch cannabis policy
- Evidence Grade:
- Well-powered twin study from a unique policy environment, though limited to a single country and self-reported data.
- Study Age:
- Published in 2010. More countries have since liberalized cannabis policy, enabling further cross-national comparisons.
- Original Title:
- Heritability of cannabis initiation in Dutch adult twins.
- Published In:
- Addictive behaviors, 35(2), 172-4 (2010)
- Authors:
- Vink, Jacqueline M(8), Wolters, Liselot M C, Neale, Michael C(6), Boomsma, Dorret I
- Database ID:
- RTHC-00460
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does legal cannabis change how much genetics matters?
In the Netherlands, where cannabis use was permitted, the genetic contribution (44%) was similar to countries where it was illegal. This suggests drug policy changes who is exposed but not how genes influence individual vulnerability.
How much of cannabis use is due to peer pressure or family?
Shared environmental factors (family, peers) accounted for 31% of cannabis initiation in this study, suggesting social influences are important but genetics explains a larger portion of individual differences.
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Cite This Study
https://rethinkthc.com/research/RTHC-00460APA
Vink, Jacqueline M; Wolters, Liselot M C; Neale, Michael C; Boomsma, Dorret I. (2010). Heritability of cannabis initiation in Dutch adult twins.. Addictive behaviors, 35(2), 172-4. https://doi.org/10.1016/j.addbeh.2009.09.015
MLA
Vink, Jacqueline M, et al. "Heritability of cannabis initiation in Dutch adult twins.." Addictive behaviors, 2010. https://doi.org/10.1016/j.addbeh.2009.09.015
RethinkTHC
RethinkTHC Research Database. "Heritability of cannabis initiation in Dutch adult twins." RTHC-00460. Retrieved from https://rethinkthc.com/research/vink-2010-heritability-of-cannabis-initiation
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.