Twin Study: Common Genetic Factors Drive Tobacco, Alcohol, and Marijuana Problem Use in Adolescents | Research

The takeaway

A large twin study found that tobacco, alcohol, and marijuana problem use in adolescents are mediated by common genetic influences, while shared environmental factors may be more substance-specific, with heritability significant for all substances except alcohol use.

Read this if you want to understand the genetic versus environmental factors in adolescent substance use.

Genetics drives problem use progression; shared environment drives initial experimentation

What the researchers found

Researchers studied 645 monozygotic twin pairs, 702 dizygotic twin pairs, 429 biological sibling pairs, and 96 adoptive sibling pairs, all aged 12-18 years. They examined genetic and environmental contributions to both substance use and problem use (1+ DSM-IV abuse/dependence symptoms).

Problem use was more heritable than simple use for all substances, confirming the hypothesis that progressing to problematic use has a stronger genetic component than initial experimentation. Heritability was significant for use and problem use of all substances except alcohol use alone.

Multivariate analyses found significant genetic correlations between all substances for both use and problem use, supporting common genetic vulnerability. However, shared environmental correlations were significant only for use (not problem use), suggesting family and peer influences drive experimentation but genetics drives progression to problems.

Why it matters

The distinction between genetics driving problem use and environment driving experimentation has important implications. Prevention efforts targeting the environment (peer pressure, availability) may effectively reduce experimentation, while identifying genetic vulnerability could help target interventions toward those most likely to develop problems.

The numbers in context

645 MZ twin pairs, 702 DZ twin pairs, 429 bio sibling pairs, 96 adoptive pairs. Ages 12-18. Heritability significant for all substances except alcohol use. Problem use more heritable than simple use. Genetic correlations significant across all substances. Shared environmental correlations significant for use only, not problem use.

How the study worked

Twin, sibling, and adoptive sibling study of 12-18 year olds from community samples. Structured psychiatric interviews assessed repeated use and problem use (1+ DSM-IV symptoms) for tobacco, alcohol, and marijuana. Univariate and multivariate biometrical model fitting with age- and sex-specific thresholds.

What this study cannot tell us

Cross-sectional assessment of a developmental process (adolescence). Twin assumptions may not fully hold for substance use (peers may differ for MZ vs. DZ twins). Age range 12-18 means some participants may not yet have developed substance problems. Cannabis-specific analyses were limited by lower prevalence.

How to read the evidence

Large twin study with multiple informative family types. Strong design for partitioning genetic and environmental influences.

When this study was published

Published in 2006. Molecular genetic studies have since begun identifying specific genetic variants associated with adolescent substance use.

The bigger picture

This study contributes to a growing understanding that substance use disorders share genetic underpinnings across substances. The age range (12-18) is particularly important because this is when most substance use initiates, and understanding the genetic versus environmental contributions at this stage could inform prevention timing.

Questions still open

Can genetic risk profiles identify which adolescent experimenters will progress to problem use? Would prevention programs be more effective if they differentiated between reducing initiation (environmental) and preventing progression (genetic vulnerability)?

Common questions

Is teen drug use genetic?

Both genetics and environment play roles, but differently at different stages. Environmental factors (family, peers) significantly influence whether adolescents try substances, but genetic factors more strongly influence whether experimentation progresses to problem use.

Are the genetic risks the same across different drugs?

Largely yes. This study found significant genetic correlations between tobacco, alcohol, and marijuana use and problem use, meaning the same genetic factors tend to increase risk across substances rather than being substance-specific.

Read the original research

Genetic and environmental vulnerabilities underlying adolescent substance use and problem use: general or specific?

Behavior genetics, 36(4), 603-15

View on PubMed ↗

Citation

Young, Susan E; Rhee, Soo Hyun; Stallings, Michael C; Corley, Robin P; Hewitt, John K. (2006). Genetic and environmental vulnerabilities underlying adolescent substance use and problem use: general or specific?. Behavior genetics, 36(4), 603-15.