Psychometric properties of the severity of the dependence scale for Khat (SDS-Khat) in polysubstance users

BACKGROUND: Current evidence suggests that the addiction on one substance may underpin or affect addiction on another in polysubstance users. However, there is no tool that has been shown to have psychometric validation for assessment of the severity of khat addiction in polysubstance users. METHODS: Polysubstance users with khat chewing habit (n = 178, age = 25.8 ± 3.6, BMI = 23.3 ± 2.8 kg/m(2)) were recruited from randomly selected houses for a cross-sectional study in Mizan, Ethiopia. The survey including severity of dependence scale for khat (SDS-khat), a brief metacognition questionnaire, and a semi-structured socio-demographics tool were administered by trained interviewers. RESULTS: There was no ceiling effect or floor effect in the SDS-Khat scores. Internal consistency was moderate (Cronbach’s alpha = 0.58). Internal homogeneity was adequate (Item-total correlations of the SDS-Khat; r ≥ 0.55). Significant negative correlations between the SDS-Khat and the metacognition (r = −.19 to −.34, p < 0.05 or p < 0.01) indicated convergent validity. The findings of exploratory factor analysis were non-unanimous with a suggestion of two models, i.e., a 2-factor and a 1-factor model, while the confirmatory factor analysis favored 1-Factor model. CONCLUSION: The SDS-Khat has adequate psychometric validity for the assessment of psychological severity of khat addiction in the polysubstance users.