A.M. Weinstein, and David A. Gorelic
Cannabis is the most frequently used illegal substance in the world [1–3]. Cannabis abuse and cannabis dependence are diagnoses recognized in the United States Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM IV)  and the WHO International Classification of Diseases, Tenth Revision (ICD-10) . In the United States, the number of individuals with disorders associated with cannabis use is twice that of any other illicit drug , with approximately 4 million adults meeting criteria for a life-time diagnosis of cannabis dependence . Relapse rates for cannabis users in treatment are comparable to those found for other drugs of abuse [7–11].