Their sociodemographic and clinical characteristics are presented in Table 1.
Psychometric properties of items
Table 2 shows the distributional data of the Q-LES-Q-SF items. None of the subjects left more than one-third of the items unanswered. The CFA with one factor model was found to have a 0.077 RMSEA [90 % CI (0.054–0.098)], a 0.968 CFI, and a 0.962 TLI, with loadings between 0.523 and 0.851. The CFA with two factors had a 0.076 RMSEA [90 % CI (0.054–0.098)], a 0.969 CFI, and a 0.963 TLI, with load- ings between 0.525 and 0.870.
The internal consistency reliability of the scale was 0.90. The test–retest reliability was determined using data from 67 participants who were administered the Q-LES-Q-SF on two occasions. At 0.88, the intraindividual correlation coefficient was markedly high, showing good reproducibility.
All items were significantly correlated to the total score, and the correlations ranged between 0.54 and 0.79 (Table 3). The latest uncommitted item on overall life
satisfaction showed a correlation of 0.73 to the total. Finally, the Q-LES-Q-SF was correlated to the PCS-12, MCS-12, and SF-12 total score at values of 0.65, 0.74, and 0.77, respectively (Table 3).
Independent sample t tests were conducted to evaluate the hypothesis that there was a difference in the mean QoL Q-LES-Q-SF scores between alcohol and opiate substance users. Alcohol-dependent outpatients presented signifi- cantly higher scores than did opiate-dependent outpatients (p = 0.002). Patients with somatic or psychiatric comor- bidities presented a poorer QoL than did those without comorbidities (52.6 vs 62.1; p = 0.01). Neither the dura- tion of addiction nor gender was significantly related to the Q-LES-Q-SF score.