Typologies of illicit drug use in mid-adulthood: a quasi-longitudinal latent class analysis in a community-based sample of twins.

Abstract

To identify drug use typologies based on substances used and persistence of use over two time points, use a genetically informed design to explore twin concordance of and genetic influence on the use typologies and compare patterns of declined/discontinued ("desistant") and persistent drug use on drug use correlates. Latent class analysis was applied to data from a cross-sectional self-report survey on current and past drug use. Use characteristics, use disorder, and psychiatric problems were compared across classes. Computer-assisted telephone interview in respondents' homes. A total of 3785 individual twins and siblings (1365 men, 2420 women; Mage =32) from the Australian Twin Registry Cohort III. A comprehensive interview assessed prior to past year and past year use of cannabis, stimulants, cocaine/crack, hallucinogens, opioids, sedatives, inhalants, dissociatives, and solvents; age of first use; opportunity to use; peer drug use; attention deficit/hyperactivity, conduct, antisocial personality, depressive, and substance use disorders; and suicidality. A five-class solution emerged: no/low use (50%), desistant cannabis use (23%), desistant party drug use (18%), persistent prescription drug misuse (4%), and persistent polydrug use (5%). Twin concordances were higher among monozygotic (k =0.30-0.35) than dizygotic pairs (same-sex k =0.19-0.20; opposite sex k =0.07), and biometric modeling suggested that the persistent polydrug use class, in particular, was highly heritable (a2 =0.94). Conduct disorder (OR=2.40), antisocial personality disorder (OR=3.27), and suicidal ideation (OR=1.98) increased persistent polydrug use risk; depression (OR=2.38) and lifetime suicide attempt (OR=2.31) increased persistent prescription misuse risk. Relative to persistent prescription drug misuse, persistent polydrug use was associated with higher rates of cannabis and stimulant use disorder (OR=6.14-28.01), younger first substance use (OR=0.82-0.83), more drug use opportunity (OR=10.66-66.06), and more drug-using peers (OR=4.66-9.20). Unique patterns of declined/discontinued ("desistant") and persistent drug use are differentially heritable and differentially associated with risk factors, psychiatric symptoms, and substance use disorder outcomes.