Under the Controlled Substances Act of 1970, marijuana was classified as a Schedule I drug because it was considered to have no “accepted medical use in treatment in the United States” (Eddy, 2010). Since then, 23 states and the District of Columbia have legalized the use of medical marijuana; over a dozen more state legislatures have recently considered medical marijuana bills.
The relationship between marijuana and mental health has received a great deal of attention from both proponents and opponents of medical marijuana legalization. Proponents argue that marijuana can be an effective treatment for bipolarism, depression, and other mood disorders (Rosenthal et al., 1996; Grinspoon and Bakalar, 1997; Zimmerman, 1999). They also argue that medical marijuana patients are able to reduce their use of painkillers, tranquilizers, and psychiatric medicines because of their use of marijuana (Lucido, 2004). Opponents, on the other hand, argue that marijuana use increases the likelihood of depression, anxiety, psychosis, and schizophrenia (Zammit et al., 2002; Henquet et al., 2004; Goldberg, 2006; Shulman, 2008). They also argue that the negative effects of marijuana are long-lasting and that users are at risk of suffering from decreased psychological well-being later in life (Green and Ritter, 2000; McGee et al., 2000).