Assessing problematic cannabis use

Abstract

Many cannabis users do not report experiencing harm from use, suggesting that not all use is cause for concern. The objective of this research is to establish a threshold beyond which cannabis use becomes problematic. Thresholds from the cannabis portion of the Alcohol, Smoking, Substance Involvement Screening Test (ASSIST) and the Cannabis Use Disorders Identification Test (CUDIT) were compared against a simple frequency of use question (daily use) for their ability to identify problematic users. Data are drawn from the 2008 Canadian Alcohol and Drug Use Monitoring Survey (n = 16,674). Effectiveness of the thresholds for predicting signs of problematic use was assessed in terms of sensitivity and specificity and in terms of positive and negative predictive values (NPV). The ASSIST (threshold of 8) and the CUDIT (thresholds of 6 and 8) outperformed the frequency measure with regards to sensitivity and specificity; the CUDIT with a threshold of 6 struck the best balance. With regards to positive predictive values, the CUDIT with a threshold of 8 revealed the highest value, whereas the daily use threshold, the CUDIT (threshold of 6 and 8) and the ASSIST (threshold of 8) revealed approximately the same NPV. Rates of harm were low for those using less than daily. Findings suggest that the CUDIT with a threshold of 6 may be best for use in population surveys when there is typically no reason to favor either sensitivity or specificity. Health care professionals may achieve greater precision using a threshold of 8 on the CUDIT.

• Screening, cannabis, problematic use

Notes

Notes

1. Three other brief cannabis screening tests have been used to assess problematic cannabis use. Thresholds on two of these assessment tools were established specifically for identifying problematic use among adolescents and young adults, rather than an adult population (Cannabis Abuse Screening Test (CAST), Legleye et al., 2007; problematic use of marijuana (PUM); Okulicz-Kozaryn & Sieroslawski, 2007). External criteria for identifying thresholds for problematic use on these tools were youth-specific; a threshold on the CAST was established using a positive score on the Problem Oriented Screening Instrument for Teenagers (the drug abuse section), and a threshold on the PUM was developed using external criteria such as lateness for school, problems with parents, etc. The third instrument, the CAGE (Cut down, Annoyed, Guilty, Eye-opener), an alcohol screening test, has also been used to evaluate problematic cannabis use. Two positive answers out of a possible four are interpreted as indicating problematic cannabis use (Midanik et al., 1998); however, the test has never been validated in its cannabis version.

2. Following Annaheim et al. (2008), sample weights and analyses that take into account design effects were not used because the primary aim of the study was analytical (associations between variables) and not descriptive (prevalence estimates).

3. The response options for one CUDIT item (i.e., difficulty stopping use once started) differed slightly from the original CUDIT response options (i.e., 0 = never, 1 = yes, but not in past 3 months, 2 = yes, in past 3 months instead of 0 = never, 1 = less than monthly, 2 = monthly, 3 = weekly, 4 = daily or almost daily). This difference in response option may have led to a misclassification of a small number of individuals.

4. To complete the original version of the CUDIT (Adamson & Sellman, 2003) participants must have used cannabis in the past 6 months, whereas to complete the ASSIST participants must have used cannabis in the past 3 months. For comparison sake, participants in this study completed questions from the CUDIT and the ASSIST if they indicated cannabis use in the past 3 months.

5. The original instrument used the term “stoned.”

6. Following Rainone, Deren, Kleinman, and Wish (1987) and Stephens, Roffman, and Simpson (1993), marijuana-only use was distinguished from marijuana + other illicit drug use when assessing harms because the latter group is considerably more likely to report harm from use. In the present sample of past 3-month cannabis users, 14.4% of those using only marijuana reported harm from use whereas 43.3% of marijuana + other illicit drug users reported at least one harm from drug use in the past 12 months.