Self-Determination As a Moderator in the Relationship Between Personality Traits and Cannabis Consumption

Introduction: Self-determination theory (SDT) is a comprehensive motivational theory that has been applied to many health-related behaviors. In spite of the fact that there are few research that tested some constructs of the SDT in the context of alcohol consumption, research that link theory with cannabis consumption are not familiar to the authors.

Methods: The aim of this research was to check the moderating role of self-determination in the relationship between some personality traits (extraversion, conscientiousness and neuroticism) and frequency of cannabis consumption among students that live in student dormitories in Zagreb, Croatia. In the sample of 438 students (37.9% males and 62.1% females; average age M=19.62; SD=0.826) that live in student dormitories in Zagreb the following instruments were applied: Self-Determination Scale (Sheldon & Deci, 1993), International Personality Item Pool (IPIP50) - extraversion, conscientiousness and neuroticism subscales; and the question on the number of days person has consumed cannabis in the lifetime. Before analysis, all the variables were centered. Hierarchical regression analysis was conducted with a number of days person consumed cannabis in a lifetime as a criterion, personality traits and self-determination as predictors in the first step and their interactions in the second step. If occurred, observed simple effects were checked with additional hierarchical analysis and the interaction effects were examined with post–hoc testing (multiple hierarchical analyses).

Results: There is a significant interaction effect of self-determination and extraversion on the frequency of cannabis consumption. The whole model explained 5.4% of variance of cannabis consumption, out of which the interaction effect explained 3.1% of variance. Among participants that were average and high in self-determination, increase in extraversion was followed with an increase in cannabis consumption, and the effect was stronger among students with higher self-determination. These effects are not present among students with low self-determination. Among these participants cannabis consumption was the same, regardless of their extraversion.

Conclusions: Findings of this research have important implications on prevention practice, since they show that students that seem to function well are not necessarily sufficiently equipped for life challenges. Results also show interesting dynamic in which self-determination, as a protective factor, in combination with extraversion, transforms into a risk factor for cannabis consumption.