Big Five Personality Traits and Illicit Drug Use: Specificity in Trait–Drug Associations

Abstract

Objective: High neuroticism, low agreeableness, and low conscientiousness are consistent correlates of drug use, though such patterns may be due to common familial influences rather than effects of personality per se. The present study aimed to explore associations of Big Five traits with various forms of drug use independent of confounding familial influences by leveraging differences within twin pairs to identify potentially causal (i.e., within-pair) effects of personality on use. Method: 980 same-sex twin pairs from the Australian Twin Registry Cohort III (Mage = 31.70, 71% female) were interviewed regarding lifetime (mis)use of cannabis, cocaine/crack, prescription and illicit stimulants, prescription and illicit opioids, sedatives, hallucinogens, dissociatives, inhalants, and solvents, and completed a Big Five inventory. Co-twin control analyses predicted the use of each drug from all traits simultaneously. Results: Individual-level analyses generally showed the expected associations of neuroticism, agreeableness, and conscientiousness with drug use. Familial effects were also somewhat generalized: high neuroticism, high openness to experience, and low agreeableness were associated with the use of several drug types. More specificity emerged for within-pair effects. High neuroticism was associated with prescription drug misuse; high extraversion was associated with cocaine/crack and stimulant use; high openness to experience was associated with cannabis use; low agreeableness was associated with cocaine/crack use and illicit opioid use; and no within-pair effects emerged for conscientiousness. Conclusions: Trait associations common across drugs may be primarily attributable to familial effects. There appears to be more drug-specific influence of personality on use with respect to potentially causal within-pair effects