In Male Twins, Whether You Try Drugs Is Partly Environmental, but Heavy Use and Dependence Are 60-80% Genetic
A study of 1,198 male twin pairs found that trying cannabis was influenced by both genes and family environment, but heavy use, abuse, and dependence were driven almost entirely by genetics with 60-80% heritability.
Quick Facts
What This Study Found
Researchers interviewed 1,198 male-male twin pairs (708 identical, 490 fraternal) from a population registry about lifetime use, heavy use, abuse, and dependence on six drug classes including cannabis.
Twin resemblance was consistently greater in identical twins than fraternal twins across all measures. For any drug use and for cannabis specifically, both genetic and family-environmental factors contributed. But for heavy use, abuse, and dependence, resemblance was caused almost entirely by genetic factors, with heritability typically ranging from 60% to 80%.
This mirrored earlier findings in female twins by the same research group. In both men and women, the family environment influenced whether someone tries drugs, but genetics overwhelmingly determines who progresses to problematic use.
Key Numbers
1,198 twin pairs (708 MZ, 490 DZ). Heritability of heavy use, abuse, and dependence: 60-80%. Six drug classes studied. Family environment contributed to initiation but not escalation.
How They Did This
Population-based twin study with 1,198 male-male twin pairs (708 MZ, 490 DZ). Personal interviews assessed lifetime use, heavy use, abuse, and dependence for cannabis, sedatives, stimulants, cocaine, opiates, and hallucinogens. Biometric model fitting estimated genetic and environmental contributions.
Why This Research Matters
Combined with the earlier female twin study (RTHC-00068), this established that the genetic architecture of substance use disorders is remarkably similar across sexes: environment shapes initiation, but genetics shapes escalation.
The Bigger Picture
These twin studies are foundational in addiction genetics. The consistent finding that escalation is more heritable than initiation across both sexes and multiple substances suggests a shared genetic vulnerability to addiction that transcends any specific drug.
What This Study Doesn't Tell Us
Twin studies assume equal environments for MZ and DZ twins. Lifetime assessments are retrospective and subject to recall bias. The registry-based sample may not represent all populations. Specific genes were not identified.
Questions This Raises
- ?Which specific genes drive the 60-80% heritability?
- ?Is there a general "addiction vulnerability" gene set or drug-specific genetic risks?
- ?Could genetic risk profiles guide prevention efforts?
Trust & Context
- Key Stat:
- 60-80% heritability for heavy drug use, abuse, and dependence
- Evidence Grade:
- A large population-based twin study with rigorous biometric modeling. Strong methodology for estimating genetic and environmental contributions.
- Study Age:
- Published in 2000. Genome-wide association studies have since identified specific genetic variants, confirming the high heritability estimates.
- Original Title:
- Illicit psychoactive substance use, heavy use, abuse, and dependence in a US population-based sample of male twins.
- Published In:
- Archives of general psychiatry, 57(3), 261-9 (2000)
- Authors:
- Kendler, K S(3), Karkowski, L M, Neale, M C(2), Prescott, C A
- Database ID:
- RTHC-00096
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Is drug addiction genetic?
Substantially. Heavy use, abuse, and dependence were 60-80% heritable in this study. Whether someone tries drugs is more influenced by environment, but escalation to problems is primarily genetic.
Is this the same for men and women?
Yes. This male twin study produced nearly identical results to an earlier female twin study by the same group, showing the genetic architecture of addiction is similar across sexes.
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Cite This Study
https://rethinkthc.com/research/RTHC-00096APA
Kendler, K S; Karkowski, L M; Neale, M C; Prescott, C A. (2000). Illicit psychoactive substance use, heavy use, abuse, and dependence in a US population-based sample of male twins.. Archives of general psychiatry, 57(3), 261-9.
MLA
Kendler, K S, et al. "Illicit psychoactive substance use, heavy use, abuse, and dependence in a US population-based sample of male twins.." Archives of general psychiatry, 2000.
RethinkTHC
RethinkTHC Research Database. "Illicit psychoactive substance use, heavy use, abuse, and de..." RTHC-00096. Retrieved from https://rethinkthc.com/research/kendler-2000-illicit-psychoactive-substance-use
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.