Searching for interactive effects in the etiology of early-onset substance use

Lisa N. Legrand, Matt McGue, William G. Iacono

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


This study sought to expand the modest literature investigating gene x environment interactions in the prediction of substance use. Our sample consisted of 591 male twins from the Minnesota Twin Family Study. Their relative genetic risk was estimated from their parents' substance-related diagnoses and their environmental risk from their affiliations at age 11 with social groups likely to either encourage or discourage substance use. At age 14, the boys' own substance use was assessed. We hypothesized both main effects and an interaction between our genetic- and environmental-risk variables in the prediction of substance use by this young age. We further theorized that the boys' inherited risk might take the form of temperament, specifically externalizing tendencies. Using regression analyses and biometrical modeling, we corroborated earlier research by finding evidence for a significant interactive effect in the etiology of substance use. Our results suggest that low levels of environmental risk may buffer against the potentially unfavorable effects of high familial risk; however, when environmental risk is high, the degree of familial risk is consequential. We were not able to support our second hypothesis; rather, temperament predicted substance use only through shared environmental factors.

Original languageEnglish (US)
Pages (from-to)433-444
Number of pages12
JournalBehavior genetics
Issue number6
StatePublished - 1999

Bibliographical note

Funding Information:
This study was supported in part by NIH Grants MH17069, AA09367, and DA05147. The authors thank Irene Elkins, Ph.D., for her assistance with clinical diagnosis data processing.


  • Early-onset substance use
  • Etiology
  • Genetic risk
  • Male twins
  • Minnesota Twin Family Study
  • Prediction
  • Temperament gene x environment interactions


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