title: Validity and reliability of a Severity of Dependence Scale for khat (SDS-khat).
abstract: OBJECTIVE
  (1) To assess psychological khat dependence and (2) to assess the validity and reliability of the Severity Dependence Scale (Gossop et al., 1995) amended for khat use (SDS-khat), in a sample of UK-resident male adult Yemeni khat chewers.
  
  
  METHODS
  A cross-sectional study using a face to face structured interview schedule was conducted amongst purposively sampled UK-resident adult Yemeni male khat chewers, aged 18 years and above, selected during random visits to places of khat sale. A factor analysis with principal components extraction was conducted to explore the construct validity of the proposed SDS-khat. Reliability of the proposed scale was assessed using test-retest and internal reliability tests. The concurrent validity of the proposed SDS-khat was assessed in relation to individual measures and a composite index of khat chewing behaviours using univariate analyses.
  
  
  RESULTS
  Two hundred and four Yemeni male adult khat chewers were interviewed. The mean score of the proposed SDS-khat was 5.52 (SD ±4.03). Forty nine percent of respondents (95% CI=43-55%) with ≤5 scores were more likely not psychologically dependent. A single factor, uni-dimensional solution identifying the five items making up the scale accounted for 52.33% of variance. The internal reliability was good (Cronbach's alpha coefficient=0.76) and the test retest intraclass correlation coefficient (ICC) was 0.93 (95% CI=0.80-0.97). Many individual aspects of the khat chewing were significantly related to the scale. Assessment of the proposed SDS-khat's concurrent validity with individual items of khat chewing identified several significant relationships (p≤0.05) whilst the composite index of khat behaviour also identified a significant relationship (OR=14.40, 95% CI=6.71-30.89). The proposed SDS-khat also correlated with self-reported reasons for khat chewing (p≤0.001, OR=3.54; 95% CI=1.80-6.96).
  
  
  CONCLUSIONS
  In this sample of Yemeni khat chewers the SDS-khat is recommended as a valid and reliable research tool for measuring psychological dependence upon khat. Further validation in other samples is indicated.
authors.affiliation: Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, 4 Newark Street, London E14AT, UK. s.salam@qmul.ac.uk
authors.forename: Saba
authors.initials: S
authors.lastname: Kassim
authors.forename: Sharif
authors.initials: S
authors.lastname: Islam
authors.forename: Ray
authors.initials: R
authors.lastname: Croucher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016739:Behavior, Addictive; D029754:Catha / Q000009:adverse effects*; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D009042:Motivation; D015995:Prevalence; D011619:Psychotropic Drugs / Q000009:adverse effects*; D015203:Reproducibility of Results; D057566:Self Report; D012720:Severity of Illness Index; D019966:Substance-Related Disorders / Q000145:classification*; D006113:United Kingdom / Q000453:epidemiology; D015006:Yemen / Q000208:ethnology; D055815:Young Adult
chemical_list: D011619:Psychotropic Drugs