Illicit Psychoactive Substance Use, Heavy Use, Abuse, and Dependence in a US Population-Based Sample of Male Twins

TLDR

Understanding individual risk differences is essential for developing prevention and treatment strategies for illicit psychoactive substance use, abuse, and dependence. The study interviewed 1,198 male twin pairs (708 monozygotic, 490 dizygotic) to assess lifetime use, heavy use, abuse, and dependence on multiple drugs, and analyzed twin resemblance using concordance, odds ratios, tetrachoric correlations, and biometrical modeling. Twin resemblance for substance use, heavy use, abuse, and dependence is substantial and greater in monozygotic than dizygotic twins, with genetic factors driving most behaviors and familial environment influencing only certain drug uses, yielding heritabilities of 60–80%.

Abstract

<h3>Background</h3> In order to develop informed approaches to prevention and treatment of illicit psychoactive substance use, abuse, and dependence, we need to understand the sources of individual differences in risk. <h3>Methods</h3> In personal interviews with 1198 male-male twin pairs (708 monozygotic and 490 dizygotic) ascertained from a population-based registry, we assessed lifetime use, heavy use, and abuse of and dependence on cannabis, sedatives, stimulants, cocaine, opiates, and hallucinogens. Twin resemblance was assessed by probandwise concordance, odds ratio, tetrachoric correlations, and biometrical model fitting. <h3>Results</h3> Twin resemblance for substance use, heavy use, abuse, and dependence was substantial, and consistently greater in monozygotic than in dizygotic twins. For any drug use and for cannabis and hallucinogen use, model fitting suggested that twin resemblance was due to both genetic and familial-environmental factors. Twin resemblance for sedative, stimulant, cocaine, and opiate use, however, was caused solely by genetic factors. With 2 exceptions (cocaine abuse and stimulant dependence), twin resemblance for heavy use, abuse, and dependence resulted from only genetic factors, with heritability of liability usually ranging from 60% to 80%. No consistent evidence was found for violations of the equal environment assumption. <h3>Conclusions</h3> In accord with prior results in studies of women, the family environment plays a role in twin resemblance for some forms of substance use in men. However, twin resemblance for heavy use, abuse, and dependence in men is largely caused by genetic factors, and heritability estimates are high.