After alcohol, cannabis is the second most widely used recreational drug in developed nations (Degenhardt & Hall, 2012). In the United States, 45% of adults report using cannabis at some point in their lives, with 12% using in the past 12 months (Substance Abuse and Mental Health Services Administration, 2012). Cannabis dependence was formerly determined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR; 4th ed., text rev.; American Psychiatric Association, 2000)1 by the endorsement of at least 3 of the following 6 criteria within a 12-month period: tolerance, use in larger quantities or for longer than intended, repeated unsuccessful attempts to quit or cut back, giving up important activities, spending excessive time acquiring or using cannabis, and recurrent use despite physical and/or emotional problems. Estimates suggest that 1.3% of the U.S. population meets the criteria for DSM-IV-TR cannabis dependence at some point during their lives (Stinson, Ruan, Pickering, & Grant, 2006). Among users, 9% qualify for dependence; of daily users, that number rises to roughly 25-50% (Hall & Degenhardt, 2009; Lopez-Quintero et al., 2011).
