Decision Making of Heavy Cannabis Users on the Iowa Gambling Task: Stronger Association with THC of Hair Analysis than with Personality Traits of the Tridimensional Personality Questionnaire

Abstract

Background: It is unclear whether impairment in decision making, measured by the Iowa Gambling Task (IGT), in addiction is substance-induced or the consequence of personality structure. Methods: Analysis of the IGT, the Tridimensional Personality Questionnaire (TPQ) and cannabinoids in hair and urine were performed in 13 cannabis users and matched controls. Results: Hair Δ⁹-tetrahydrocannabinol (THC) correlated negatively with the last subtrial (cards 80–100) of the IGT (R = –0.67). In all participants (n = 26) the TPQ dimension, harm avoidance, correlated negatively with the total IGT score (R = –0.46). The last IGT-subtrial correlated with adventure seeking (R = 0.43), harm avoidance (R = –0.39) and reward dependence (R = –0.44). The last subtrial gives information on whether a participant has learned the IGT strategy. Multiple regression confirmed the impact of THC on the last subtrial, whereas TPQ personality traits did not additionally explain variance. Conclusions: Former indications of the IGT performance depending on the amount of cannabis consumed were replicated with an objective measurement of chronic cannabis consumption (hair THC). Multiple regression analysis argues for a stronger impact of chronic THC consumption than personality traits, but does not provide a causal relationship. Other factors (e.g. genetic) may also play a role.