Motives of celebration, coping, and social anxiety are significantly associated with symptoms of anxiety at p ≤ 0.05. Only coping remains significantly associated with symptoms of anxiety using the Bonferroni corrected p ≤ 0.003. Coping is positively and significantly associated with symptoms of anxiety whereas the more often marijuana use is motivated by coping, the higher the score for symptoms of anxiety. The magnitude of the association of motives of coping with symptoms of anxiety is of almost 1 indicating that for any one unit change in the strength of coping motive there is almost a one point change in scores of symptoms of anxiety. Post hoc power analyses indicate that the statistical power greater than 0.99. Results from the mediation analysis with past 90 days marijuana use as a mediator are presented in Tables 4.45a-d. There is no evidence of any indirect effects of motives of marijuana use on symptoms of anxiety through past ninety days marijuana use. All 95% bootstrap confidence interval for the indirect effect, based on 10,000 bootstraps, include zero. There is however evidence of a positive direct effect with symptoms of anxiety for motives of coping and social anxiety, independent of past 90 days use. Results from the mediation analysis with daily number of hits as a mediator are presented in Tables 4.46a-d. All 95% bootstrap confidence interval for the indirect effect, based on 10,000 bootstraps, include zero. There is, however, evidence of a negative direct effect with symptoms of anxiety for motive of celebration and a positive direct effect for motives of coping and social anxiety. After controlling for age, gender, user group, and race/ethnicity, there is a negative direct effect between motives of marijuana use and symptoms of anxiety for motives of celebration and sleep,vertical grow systems and a positive direct effect for motives of coping and social anxiety. Table 4.47 presents the regression estimates without and with control variables.

Motives of marijuana use account for approximately 24% of the variance of overall psychological distress. Motives of celebration, coping, conformity and social anxiety are significantly associated with overall psychological distress at p ≤ 0.05. Only coping remains significantly associated with overall psychological distress using the Bonferroni corrected p ≤ 0.003. Coping is positively, significantly associated with overall psychological distress whereas the more often marijuana use is motivated by coping the higher the score for psychological distress. The magnitude of the association of motives of coping with psychological distress is of approximately 3 indicating that for any one unit change in the strength of coping motive there is almost a three-point change in scores of symptoms of anxiety. Post hoc power analyses indicate that the statistical power greater than 0.99.Results from the mediation analysis with past 90 days marijuana use as a mediator are presented in Tables 4.48a-d. There is no evidence of any indirect effects of motives of marijuana use on overall psychological distress through past 90 days marijuana use. All 95% bootstrap confidence interval for the indirect effect, based on 10,000 bootstraps, include zero. There is however evidence of a positive direct effect with overall psychological distress for motives of coping and social anxiety, and evidence of a negative direct effect for motives of celebration and conformity. The negative direct effect with celebration is no longer significant after controlling for gender, age, user group, and race/ethnicity. Results from the mediation analysis with daily number of hits as a mediator are presented in Tables 4.49a-d. There is no evidence of any indirect effects of motives of marijuana use on overall psychological distress through daily number of hits. All 95% bootstrap confidence interval for the indirect effect, based on 10,000 bootstraps, include zero. There is however evidence of a negative direct effect with psychological distress for motives of celebration and conformity, and a positive direct effect for motives of coping and social anxiety.

When controlling for age, gender, user group, and race/ethnicity, the negative direct effect between motives of marijuana use and psychological distress for motives of celebration and conformity remains as well as the positive direct effect for motives of coping and social anxiety. Gender was found to moderate the association between social anxiety motives of use and symptoms of depression when tested with and without control variables. The addition of the interaction term between the motive of social anxiety and gender explained a significant increase in variance for symptoms of depression ∆R2 = 0.012, p < 0.05 for the model without control variables, and ∆R2 = 0.014, p < 0.05 for the model with control variables. The interaction was probed by testing the conditional effect of the social anxiety motive of use on symptoms of depression for both men and women. For women, but not men, the motive of social anxiety was significantly associated with more symptoms of depression . Furthermore, the slope of the interaction term indicates that women scored higher on symptoms of depression than men at the average level of the social anxiety motive. When analyzed with and without control variables, gender was found to moderate the associations for the motives of experimentation and availability with symptoms of anxiety. The addition of the interaction term between the motive of experimentation and gender explained a significant increase in variance for symptoms of anxiety: ∆R 2 = 0.012, p < 0.05. The addition of the interaction term between the motive of availability and gender explained a significant increase in variance for symptoms of anxiety: ∆R2 = 0.01, p < 0.05. Probing of the interactions, for both motives of experimentation and availability, however yielded no significant conditional effect for neither men or women. Conditional effects for motives of experimentation are as follows: This could therefore indicate a crossover interaction where there is no overall effect of either motives of use or gender on symptoms of anxiety. In both cases, the effect of gender on symptoms of anxiety is opposite, depending on the value of motives of use.

Although gender was initially found to moderate the association between motives of boredom and symptoms of anxiety, the interaction was no longer significant following the addition of control variables. When analyzed with and without control variables, gender was found to moderate the association for the motive of social anxiety with overall psychological distress. The addition of the interaction term explained a significant increase in variance for psychological distress ∆R2 = 0.010, p < 0.05. The interaction was probed by testing the conditional effect of social anxiety for both men and women. For women, but not men, the motive of social anxiety was significantly associated to overall psychological distress . Furthermore, the slope of the interaction term indicates that women score higher on psychological distress than men at the average level of social anxiety motive. Although gender was initially found to moderate the association between motives of boredom and psychological distress, and motives of availability with psychological distress, these interactions were no longer significant following the addition of control variables. The purpose of this dissertation was to determine the associations between motives of marijuana use and symptoms of depression, symptoms of anxiety, and overall psychological distress in a sample of young adults who use marijuana for medical and/or recreational reasons. Furthermore, I sought to establish whether these associations differ by gender. As marijuana use is common and on the rise amongst young adults , and as young adulthood is a period of increased mental health vulnerabilities , it is urgent to disentangle the potential effects of marijuana use on the mental health of young adults, particularly because mental health in young adulthood is the strongest predictor of mental health in adulthood .The work presented in this dissertation advances our understanding of motives of marijuana use as well as the associations between motives of marijuana use and symptoms of depression, symptoms of anxiety, vertical grow rack and overall psychological distress in young adults who use marijuana for medical and/or recreational reasons. The purpose of the first aim was to confirm the factor structure of the motives of marijuana use questionnaire used to study motives of marijuana use in young adults of Los Angeles who use marijuana for medical and/or recreational reasons. It was hypothesized that from the fifty-one-item questionnaire, seventeen motives of marijuana use would emerge. Twelve of these motives would replicate those found by Lee et al. in their study to develop and validate a comprehensive marijuana motive questionnaire. The other five motives to be confirmed would be the medical use motives drafted by the CHAYA team. Furthermore, it was hypothesized that there would be no gender differences in the factor structure of motives of marijuana use. The best fitting and most psychometrically sound factor structure for motives of marijuana use for this sample was the originally hypothesized seventeen factor structure composed of Lee et al.’s twelve motives and the five medical motives drafted by the CHAYA team.

The final twelve non-medical items are: boredom, availability, coping, conformity, experimentation, alcohol, celebration, altered perceptions, social anxiety, relative low risk, and sleep. The final five medical motives are: pain, nausea, substitution, natural remedy, and attention. Following and extending Cooper’s Motivational Model of Use , these motives can be conceptualized as motives promoting positive experiences, motives to avoid negative experiences, and medical use motives. Motives that promote positive experiences are motives of celebration, altered perceptions, experimentation, enjoyment, alcohol, relative low risk, and, availability. Motives for avoidance of negative experiences are motives of coping, conformity, sleep, boredom, and social anxiety. Medical motives are motives of attention, substitution, natural remedy, pain, and nausea. These seventeen motives proved to be consistently well fitting, stable over time, and gender invariant when tested using both wave 1 and 2 data. Although these findings need to be replicated using a random sample, the Amended Comprehensive Marijuana Motive Questionnaire, is the first to integrate both recreational and medical motives of use. Given the high rates of overlap between recreational and medical use , the validation of such an instrument, and its stability over time and across gender, will allow for a more accurate assessment of motives of marijuana use. To date, neither gender invariance for the motives from the Comprehensive Marijuana Motive Questionnaire nor endorsement of motives by gender had been examined. Interestingly, in this sample, except for the motives of experimentation and boredom, the reporting trend was higher for women compared to men. There were also significant differences in mean scores of reported motives of use between men and women for motives of attention, celebration, enjoyment, natural remedy, nausea, pain, sleep and social anxiety. This indicates that women endorse any given motive more strongly than men do. As discussed in Chapter 2, the gap in marijuana use prevalence between men and women is closing . Additionally, in line with gender socialization and changing gender norms, whereas marijuana use was considered acceptable for men but less so for women, it is now increasingly considered acceptable behavior for women . These changes in norms and behaviors may be starting to reflect in data collected. With that said, it is important to note that these preexisting differences between genders may be a confounding factor for causal inferences and reflect the unbalanced nature of our sample due to it being nonrandom rather than a true reflection of patterns within the population. The work presented in this dissertation also advances our understanding of the associations between motives of marijuana use and mental health outcomes in a sample of young adults who use marijuana heavily for medical and/or recreational reasons. It does so by: 1) replicating previous findings for the coping motive of use whereas the more an individual endorses coping motives of use, the poorer the associated outcomes are; 2) extending knowledge with regards to indirect effects of motives on mental health outcomes through frequency of use; and 3) establishing that some of the associations between motives of use and mental health outcomes vary by gender. The second and third aims of this dissertation were to investigate the associations between motives of marijuana use and symptoms of depression, symptoms of anxiety, and overall psychological distress, and to determine whether these associations varied by gender in a sample of young adults who use marijuana for medical and/or recreational reasons in a context of legalized medical marijuana.