The structure of psychological distress.

In this study we describe the factor structure of the Psychological Distress Index used in the Quebec Health Survey and compare a model that includes psychophysiologic symptoms (29 items) with a model restricted to cognitive and affective symptoms only (18 items). Three samples (n = 2,000) were used to test the likelihood of these two models. Confirmatory factor analyses were carried out using LISREL VII. Logistic regression was then used to examine the association of the two versions with demographic variables and health indicators. Analysis indicates that both versions show satisfactory construct validity. Except for age, the associations observed between both versions and respondents' demographic characteristics are similar; however, the 29-item version is more strongly associated with health status indexes, suggesting a possible bias attributable to somatic items.