Individual differences in the risk for cannabis use and cannabis use disorder appear to be linked to genetic risks associated with antisocial and borderline personality disorder traits, according to the results of a study published in Addiction.
Nathan Gillespie, PhD, of the Virginia Institute for Psychiatric and Behavioral Genetics at Virginia Commonwealth University in Richmond, and colleagues analyzed cross-sectional data from 1419 Norwegian adult twins who were interviewed between 1999 and 2004 as part of a population-based study of mental health. The records contained complete personality disorder and cannabis data. Personality disorder, lifetime cannabis use, and cannabis use disorder were based on Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria.
The investigators found that antisocial (β=0.23) and borderline (β=0.20) personality disorders were strongly associated with cannabis use as well as with cannabis use disorder (β=0.26 and β=0.12, respectively) after adjusting for age and sex. Genetic risks associated with traits for both of these disorders explained 32% to 60% of the total variance in cannabis use and cannabis use disorder. Dependent and avoidant personality disorders explained 11% and 16% of the total variance in cannabis use and cannabis use disorder, respectively.
The researchers noted that to their knowledge, this is the first study to investigate all 10 personality disorders and explore associations with cannabis use and use disorder within the context of genetics. The data showed the strongest association with the borderline and antisocial phenotypes. They also found that these phenotypes and genotypes showed the greatest liability to lifetime alcohol use and alcohol use disorder, suggesting that alcohol and cannabis use and misuse share many of the same genetic and environmental risk factors.
The investigators argue that the genetic covariance between alcohol and cannabis use and misuse as well as other psychoactive substances is likely being captured by the same genetic risks in borderline and antisocial personality disorder trait score. In contrast, schizoid and dependent personality disorder traits had little association with cannabis use.
Gillespie NA, Aggen SH, Neale MC, et al. Associations between personality disorders and cannabis use and cannabis use disorder: a population-based twin study [published online March 3, 2017]. Addiction. doi:10.1111/add.14209