Marijuana and Anxiety

"Several studies have linked marijuana use to increased risk for psychiatric disorders, including psychosis (Schizophrenia), depression, anxiety, and substance use disorders, but whether and to what extent it actually causes these conditions is not always easy to determine. The amount of drug used, the age at first use, and genetic vulnerability have all been shown to influence this relationship. The strongest evidence to date concerns links between marijuana use and psychiatric disorders in those with a preexisting genetic or other vulnerability."
 
-National Institute on Drug Abuse