Psychometric properties of the CAST and SDS scales in young adult cannabis users

Aim: To assess the validity of two cannabis use severity scales among young cannabis users and to evaluate their ability to detect Substance Use Disorders (SUD). Participants: 241 volunteers (18-25 years), with a wide spectrum of cannabis use in the last 12 months. Measurements: The Cannabis Abuse Screening Test (CAST) and Severity of Dependence Scale (SDS) were self-administered. The Psychiatric Interview for Substance and Mental Disorders (PRISM) was used as gold standard for cannabis use disorders according to DSM-IV. Reliability and validity were assessed for two different CAST coding algorithms (b-binary and f-full) and for the SDS. In addition, the cannabis use diagnostic criteria contained in the PRISM were grouped to approximate forthcoming proposed DSM-V criteria to further evaluate these scales. Findings: 26.6% (95% Cl: 21.0-32.2) of the subjects met criteria for cannabis dependence, and 49.0% (95% Cl: 42.7-55.3) for cannabis use disorders. For both scales internal consistency (Cronbach's alpha>0.71) and test-retest intraclass correlation coefficients (>0.80) were good. The score 12 in the CAST-full discriminated better than others between presence and absence of dependence (27.0%; 95% Cl: 21.4-32.6) while the score for discrimination of SUD was 9 (51.5%; 95% Cl: 45.1-57.8). For the SDS the values were 7 (22.0%; 95% Cl: 16.8-27.2) and 3 (64.7%; 95% Cl: 58.7-70.8), respectively. According to proposed DSM-V criteria, for moderate and severe addiction the values for the CAST-f were 7 (68.5%; 95% Cl: 62.5-74.3) and 12 (27%; 95% Cl: 21.3-32.6) and for the SDS, 3 (65.0%; 95% Cl: 58.7-70.8) and 7 (22%; 95% Cl: 17.0-34.3), respectively. Conclusions: The CAST and SDS applied to young cannabis users are reliable and valid measures to detect cannabis use disorders when compared to both DSM-IV and proposed DSM-V criteria. (C) 2012 Elsevier Ltd. All rights reserved.