Reliability and validity of the severity of dependence Scale in a Chinese sample of treatment-seeking ketamine users

Objective: Despite growing popularity of ketamine misuse in Asia, there is a lack of a validated instrument to measure the severity of ketamine dependence. Psychometric properties of Chinese Severity of Dependence Scale for ketamine (C-SDS-K) were examined in a sample of treatment-seeking ketamine users in Hong Kong. Methods: A total of 80 treatment-seeking ketamine users were recruited from 3 treatment centres. The C-SDS-K was administered to assess their severity of dependence on ketamine in the previous month. The diagnosis of their ketamine misuse as per the DSM-IV criteria, and the count of dependence criteria fulfilled in the previous month were determined by the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). Results: The C-SDS-K showed high internal consistency (α = 0.74) and test-retest reliability (intraclass correlation coefficient = 0.95). Total score of C-SDS-K correlated positively with frequency (rs = 0.73, p < 0.001) and dose (rs = 0.89, p < 0.001) of ketamine use per week in the previous month, duration of regular ketamine use (rs = 0.28, p = 0.01), and the count of DSM-IV ketamine dependence criteria met in the previous month (rs = 0.84, p < 0.001). All items loaded strongly on a single factor (factor loading ≥ 0.60) in principal component analysis. Conclusion: The findings support SDS as a reliable and valid tool for measuring the severity of dependence in the treatment-seeking population of Chinese ketamine users.