Evaluating the Psychometric Properties of the Severson 7-Item Smokeless Tobacco Dependence Scale (SSTDS)

The objective of the study was to assess the psychometric properties of the Severson 7-item Smokeless Tobacco Dependence Scale (SSTDS).

Data from 95 male exclusive smokeless tobacco (ST) users were obtained through a self-administered mail survey to evaluate the reliability and validity of the SSTDS. Reliability of the scale was assessed by measures of internal consistency including Cronbach's coefficient alpha and item-total correlation. Other ST dependence scales and salivary cotinine concentration were used to evaluate concurrent validity. Structure model of the scale was ascertained by exploratory factor analysis. Overall accuracy and optimal cutoff score were obtained to evaluate SSTDS as a screening tool for ST dependence.

The SSTDS had high reliability as assessed by the internal consistency coefficient (ordinal α = 0.83). SSTDS total score was significantly correlated with Fagerström Test for Nicotine Dependence for ST users-FTND-ST (r = 0.42) and modified Tobacco Dependence Screener-TDS (r = 0.58). Exploratory factor analysis of the SSTDS identified two underlying factors measuring distinct dimensions of dependence. With reference to TDS based dependence diagnosis, SSTDS demonstrated good diagnostic accuracy (area under the curve: 0.82, 95% confidence interval: 0.74-0.90). Salivary cotinine concentration was not associated with the total score of the SSTDS; however, at an optimal cutoff score of SSTDS >9, everyday ST users classified as dependent had significantly higher cotinine concentration.

SSTDS is a reliable measure of dependence that has higher concurrent validity and reliability as compared with other commonly used ST dependence scales. Further research is needed using a larger and more diverse sample of ST users to unequivocally establish the validity of the scale.

ST dependence has multiple aspects that can be best studied by multidimensional dependence scales. The study findings validate that the SSTDS measures not only the physical dependence but also the behavioral and psychological dimensions of dependence. Good psychometric properties, diagnostic accuracy, and multidimensional structure of SSTDS indicate that it may serve as an effective tool in assessing ST dependence in clinical and research settings.