According to the most recent data from Monitoring the Future
, in 2006 close to one in three (30.2%) college students had used cannabis in the past year (Johnston, O’Malley, Bachman, & Schulenberg, 2007
). These prevalence estimates are similar to findings from the 2001 Harvard College Alcohol Study
(Mohler-Kuo, Lee, & Wechsler, 2003
), which reported that 30% of college students used cannabis in the past year. Moreover, as with other forms of illicit drug use, young adults consistently have a higher prevalence of cannabis use than other age groups (Substance Abuse and Mental Health Services Administration [SAMHSA], 2006
), and college students appear to be no different from their non-college-attending peers in this respect (Johnston, O’Malley, Bachman, & Schulenberg, 2006
Considering the widespread use of cannabis among college students, it is surprising that epidemiologic data on cannabis use disorders in this subpopulation are scarce. Cannabis use disorders (CUD) encompass the two distinct diagnoses of abuse and dependence, defined in the DSM-IV by the same criteria as for other substance use disorders (American Psychiatric Association [APA], 1994
). As compared to other age groups, young adults are known to have the highest past-year prevalence of CUD (5.9%), owing in part to their correspondingly high prevalence of cannabis use (SAMHSA, 2006
). To our knowledge, however, no studies have measured CUD prevalence among young adults attending college. Anthony et al. (1994)
analyzed data from the National Comorbidity Survey
and observed a substantially higher lifetime prevalence of cannabis dependence among adolescent and young-adult cannabis users as compared to older users. More recent results from another national epidemiologic study indicate that approximately one in three past-year cannabis users in the general population meets criteria for CUD (Compton, Grant, Colliver, Glantz, & Stinson, 2004
), however estimates for college-attending young adults were not reported. As yet, it is unknown whether cannabis-using college students experience a risk for CUD that is similar to other young adults.
Aside from the risk for CUD, an extensive body of literature has described other adverse effects of cannabis use, and while most long-term effects appear to be limited to heavy or chronic use, important short-term effects occur during the acute phase of intoxication, regardless of the frequency of use (see reviews by Budney, Moore, & Vandrey, 2004
; Joy, Watson, & Benson, 1999
; Kalant, 2004
). Neurocognitive impairments—such as problems with psychomotor function, attention, memory, and learning—occur during intoxication, some of which persist after a brief period of abstinence. The possible functional consequences of these effects are an important area of concern, as they have the potential to affect the large number of individuals who use cannabis moderately or occasionally. However, most prior evidence of the adverse effects of cannabis use stems from clinical and experimental studies, whereas epidemiologic data about the proportion of cannabis users who experience specific effects has been limited.
Several prior studies of college students have investigated cannabis-related problems and warrant mention here. In one study, the number of cannabis-related problems significantly increased during the transition from high school to college (White, Labouvie, & Papadaratsakis, 2005
), but data on discrete cannabis-related problems were not presented. In another study of alcohol-using college students, use of cannabis significantly increased the risk for experiencing any substance-related problems, even controlling for heavy drinking and demographics (Shillington & Clapp, 2001
). Other studies of college students have linked cannabis use to specific health risk behaviors, such as smoking tobacco (Hammersley & Leon, 2006
; Tullis, Dupont, Frost-Pineda, & Gold, 2003
) and unsafe driving practices (Everett, Lowry, Cohen, & Dellinger, 1999
). These studies have had limited generalizability, and none were designed to estimate prevalence or assess CUD. Nevertheless, they demonstrate the public health significance of this issue and draw attention to the need for a more complete understanding of the types of problems associated with cannabis use among college students.
By definition, individuals with CUD experience functional problems in their lives as a result of their cannabis use, such as loss of major role functions and repeated legal problems (APA, 1994
). While the DSM-IV criteria are helpful in identifying individuals with the most serious risk for cannabis-related problems, prior evidence suggests that a substantial number of problematic users are overlooked by these definitions (Degenhardt, Lynskey, Coffey, & Patton, 2002
). Therefore, more research is warranted to describe the prevalence of cannabis-related problems experienced by cannabis users who fall below the threshold of CUD (i.e., “diagnostic orphans”) and identify how they may differ from CUD cases.
In any study of drug users, it can be difficult to disentangle the consequences of cannabis use from those of other substances, especially in light of the high prevalence of polysubstance use among cannabis users (Gledhill-Hoyt, Lee, Strote, & Wechsler, 2000
). Prior evidence suggests that cannabis users are more likely to experience CUD and other cannabis-related problems if they are also heavy drinkers and/or cigarette smokers (Chen, O'Brien, & Anthony, 2005
; Degenhardt et al., 2002
). Whether this association between CUD and drinking and smoking tobacco holds true for college students is unknown.
The present study attempts to address the gap in the literature on cannabis-related problems among college students. Using data from a large cohort of systematically sampled first-year college students, the present study aims to: 1) estimate the prevalence of CUD; 2) determine the proportion of users who meet criteria for dependence; 3) describe the occurrence of cannabis-related problems among cannabis users; and 4) determine whether CUD cases differ from “diagnostic orphans” and non-problematic cases with respect to cannabis-related problems and intensity of use. Additionally, as a post-hoc analysis, we compared the prevalence of CUD and cannabis-related problems amongst light vs. heavy drinkers and tobacco cigarette smokers vs. non-smokers.