Background: Shared genetic underpinnings may partially account for the observed comorbidity between cannabis use and depression. Both cannabis and depression also impact cognitive functioning, and are associated with poorer academic outcomes for college students. In the current study, we examined the degree to which familial risk for drug problems and depression or anxiety increase the risk of cannabis use and depression and impact academic outcomes.
Methods: Participants included 9,886 freshman students from the Spit for Science (S4S) study. S4S is a longitudinal study of genetic and environmental influences on substance use and emotional health outcomes in college students. Familial risk scores were estimated using self-reported family history (FH) of drug problems and FH of depression or anxiety. We hypothesized that: (1) FH of drug use predicts both higher lifetime cannabis use and depression; (2) FH of depression-anxiety predicts both depression and cannabis use; and (3) cannabis use and depression predict lower GPA. Structural equation modeling was implemented in OpenMx to estimate the direct and indirect effects of FH of drug use and FH of depression/anxiety on cannabis use, depression, and freshman year GPA.
Results: We observed significant direct effects of familial risk of drug use on cannabis use (β=0.155, [0.123, 0.187]) and GPA (β=-0.062, [0.092, -0.033]), but not depression. We also observed significant direct effects of familial risk of depression-anxiety on depression (β=0.388, [0.356, 0.420]), cannabis use (β=0.217, [0.184, 0.250]), and GPA (β=0.059, [0.024, 0.093]). Cannabis use was negatively associated with GPA (β=-0.187, [-0.213, -0.161]), but there was no direct effect of depression on GPA. Further, FH of drug use was indirectly associated with lower GPA via cannabis use (β=-0.029, [-0.037, -0.022], and FH of depression-anxiety was indirectly associated with lower GPA via cannabis use (β=-0.041, [-0.050, -0.033].
Conclusions: Our findings support our hypotheses that FH of drug use is associated with greater cannabis use, greater depressive symptoms, and lower GPA both directly, and indirectly through cannabis use. However, while FH of depression-anxiety was associated with greater depressive symptoms and cannabis use, we observed no indirect effect of depression on GPA. We plan to expand upon these analyses to include polygenic scores for depression and cannabis use. These findings contribute to understanding of the genetic relationship between cannabis use and depression, while also investigating the potential impact of these factors on college student performance.
References
Arria, A. M., Caldeira, K. M., Bugbee, B. A., Vincent, K. B., & O’Grady, K. E. (2015). The academic consequences of marijuana use during college. Psychol Addict Behav, 29(3), 564-75.
Dick, D. M., Nasim, A., Edwards, A. C., Salvatore, J. E., Cho, S. B., Adkins, A., ... & Goyal, N. (2014). Spit for Science: launching a longitudinal study of genetic and environmental influences on substance use and emotional health at a large US university. Frontiers in genetics, 5.
Smolkina, M., Morley, K. I., Rijsdijk, F., Agrawal, A., Bergin, J. E., Nelson, E. C., ... & Lynskey, M. T. (2017). Cannabis and depression: a twin model approach to co-morbidity. Behavior genetics, 47(4), 394-404.
Cognition: Education, Intelligence, Memory, Attention , Psychopathology (e.g., Internalizing, Externalizing, Psychosis) , Substance use: Alcohol, Nicotine, Drugs
