Disentangling the Association Between Personality Traits and Cannabis Use and Disorder in Cannabis Users of European Ancestry Öffentlichkeit

Abstract

Cannabis use (CU) and use disorder (CUD) are associated with poor health and behavioral outcomes. Past research has reported that lifetime CU and CUD are becoming increasingly prevalent and are associated with poor behavioral outcomes. Individuals with low levels of conscientiousness and openness to experience, and high levels of agreeableness are at increased risk for CU and CUD. However, it is unclear whether the association between personality and CU and CUD is due to shared genetic or environmental factors. Twin studies have found that CU and CUD are heritable with estimates of 61% and 78% respectively. Genome-wide association studies (GWASs) have also found some single-nucleotide polymorphisms (SNPs) to be associated with CU and CUD. Likewise, personality traits have heritability estimates ranging from 41 to 61%, and a GWAS has found that one single nucleotide polymorphism (SNP) is associated with conscientiousness. Based on these observations, the current study examined whether personality traits, which are evident early in life, mediate some of the genetic effects on CU and CUD independent of known polygenic risk for these behaviors. Analyses used data from Wave IV of the National Longitudinal Study of Adolescent to Adult Health (Add Health). Lifetime repeated CU was operationalized by asking if participants had used cannabis five or more times within their lifetime. Add Health used the DSM-IV and assessed CUD through cannabis abuse and dependence. CUD severity was operationalized as a sum score of symptoms endorsed. Personality was measured using the Mini-International Personality Item Pool. Genetic effects were evaluated using polygenic risk scores (PGSs) that were created using summary statistics provided by GWASs for personality, CU, and CUD. We found that low levels of conscientiousness were associated with CUD severity; none of the PRSs predicted their respective phenotype and there was limited evidence for indirect effects of personality PGSs on the cannabis outcomes. These findings contradict our hypotheses and suggest that personality may be more related to initiation of use (not investigated here) rather than severity of use and problems. Future studies should examine cannabis initiation as an outcome variable and consider genome-wide approaches for deriving a PGS.

Table of Contents

Introduction.…………………………………………………………………………………...…..1

Methods……………………………………………………………………………………………6

            Participants……………………………………………………………………………...…6

            Measures…………………………………………………………………………………..6

Genotyping, quality control, and genetic imputation………………….…………………10

Analytic Strategy……………………………….………………………….…………….11

Results………………………………………………………………………………..…………..15

            Descriptive Statistics………………………………………….………………………….15

            Zero-Order Correlations………………………………………………………………….15

            Direct and Indirect Associations Between Personality PGS, Personality, and Cannabis 

Outcomes………………………………………………………..……………………….16

Direct Polygenic Effect on Cannabis Outcomes……………………...………………….17

Discussion………………………………………………………………………………………..17

            Limitations…………………………….…………………………………………………20

            Implications………………………………………………………………...…………….20

            Conclusions & Future Directions…………………………….…………………………..21

References……………….………….……………………………………………………………23

Tables & Figures…………………………………………………………………………………30

            List of Tables & Figures…………………………………………………………………30

            Table 1………………..………………………………………………………………….32

            Table 2…………………….…………………………….……………………………….33

Table 3…………………………………………..……………………………………….34

Table 4……………………..…………………………………………………………….35

Table 5………………………………………………………………………………..….36

Table 6……………………………………………………………………………..…….37

Table 7………………………………………………………………………………..….38

Table 8……………………………………………………………………………..…….39

Figure 1………………………….……………………………………………………….40

Figure 2………………………….……………………………………………………….41

Figure 3………………………….……………………………………………………….42

Figure 4………………………….……………………………………………………….43

Figure 5………………………….……………………………………………………….44

Figure 6………………………….……………………………………………………….45

Figure 7………………………….……………………………………………………….46

Appendices…………………………………………………………………………….…………47

            Appendix A……………………..………………………………………………………..47

            Appendix B……………………..………………………………………………………..49

About this Honors Thesis

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School	Emory College
Department	Psychology
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Personality Psychology, Psychobiology
Stichwort	Personality Genetics Cannabis
Committee Chair / Thesis Advisor	Rohan Palmer, Emory University
Committee Members	John Lindo, Emory University Jessica Barber, Emory University

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