Adolescents who had more symptoms of depression in ninth grade were quicker than their peers to engage in smoking cigarettes and use marijuana and hard drugs across the high school years, according to a longitudinal study in the February 2012 issue of the Journal of Adolescent Health.
Depression often has its onset in adolescence, which is also when individuals are more likely to increase risky health behaviors, such as alcohol and marijuana use. In the past, researchers had two divergent hypotheses to explain the relationship between depressive symptoms and risky behaviors in adolescents: the self-medication/acting out hypothesis, which holds that early depressive symptoms predict increases in risky behaviors over time, and the failure hypothesis, which states that early participation in risky behaviors predicts increases in depressive symptoms over time.
Given a lack of consensus as to which hypothesis is accurate, Setareh Hooshmand, a graduate student in the department of psychology at Brock University, St. Catharines, Ont., and her coinvestigators wanted to examine which of these appeared correct. In a cohort sequential study, they followed 4,412 adolescents (51% male) aged 14-17 from grades 9 to 12 (J. Adolesc. Health 2012;50:140-7). Trained research staff administered a questionnaire to students that asked about depressive symptoms, frequency of alcohol use, number of alcoholic drinks at a time, cigarette smoking, marijuana use, hard drug use, and delinquency rates.
The results indicate support for the self-medication hypothesis, the researchers said. Specifically, those individuals who had more depressive symptoms in ninth grade reported faster increases than their peers in smoking, marijuana, and hard drug use – all of which might be perceived as having mood-enhancing functions – across the high school years.
The self-medication hypothesis, however, was not supported for the relationships between depressive symptoms and alcohol use, and depressive symptoms and delinquency, the researchers say. Alcohol use, though sometimes a form of self-medication, often increases over the high school years, and might represent enhanced social networks and feelings of belonging, the researchers say. Delinquent behaviors often occur in the presence of friends, suggesting heightened arousal rather than depression.
The study results show no support for the failure hypothesis. "The failure hypothesis assumes that depressive symptoms would result from risk behaviors because of an internalization of social rejection," the researchers say. "Participating in substance-related risks, however, may not lead to social rejection from peers for adolescents. In fact, socially-accepted substance use, such as alcohol use, often occurs in social contexts and thus may help alleviate feelings of rejection and low self-esteem."
The study’s limitations are that they cannot infer causality and that other variables, such as genetic and/or environmental influences, might better explain the relationship between depressive symptoms and risky behavior. Also, this relationship might be dynamic and change over adolescent development, suggesting the need for research at different age periods.
Despite these limitations, the researchers say, the results are important. "They suggest that by targeting depressive symptoms during early adolescence, treatment programs may prevent increases in the frequency of health-risk behaviors over the course of high school," the researchers say.
Teena Willoughby, Ph.D., the second author, received funding from the Social Sciences and Humanities Research Council of Canada.