Consequences of Marijuana Use for Depressive Disorders
The purpose of this study is to investigate the temporal order in the association between marijuana use and depression. There are two possible hypothesis examined, and for each of them is conducted a separate set of analyses. The dependent variable in the first hypothesis is current depression, predicted by previous and current marijuana use, abuse, and dependence. In the second hypothesis the dependent variables are current marijuana use, abuse, and dependence, predicted by previous and current depression.
To conduct the analyses this study uses data from the National Comorbidity Survey (NCS). The NCS is an epidemiological research study of the prevalence, causes, and consequences of psychiatric disorders and comorbodity, analyzing data from a national sample of 8098 participants covering an age range from 15 to 54 years old.
Results show that prior depression is the main predictor of current depression while marijuana use has a weak effect on current depression. Marijuana users are slightly more depressed than never users, but the lag of the effect is short. There is a strong association between marijuana use and abuse and other drug use and abuse. Findings show that prior marijuana and other drug use and abuse predict current marijuana use and abuse. There is a weak association between current depression and current marijuana use, and when controlled for prior marijuana use this association disappears. The results of this study provide no support for the coping theory. There is a clear pattern of comorbidity of both, mental disorders, and substance use and abuse.