The factor structure of the BDI in facial pain and other chronic pain patients: A comparison of two models using confirmatory factor analysis

Objectives. 1) To compare two measurement models of the BDI in chronic pain sufferers to see which provides the better fit; 2) to assess whether model fit differs for a facial pain sample compared to a sample of pain sufferer s attending a multidisciplinary pain clinic; and 3) to establish which affe ctive and somatic sub-scales of the BDI could be used in chronic pain resea rch. Design. Two groups of chronic pain sufferers, a facial pain group, and a gr oup attending a multidisciplinary pain clinic completed self-report questio nnaires on pain (Multidimensional Pain Inventory), depression (BDI), and me asures of anxiety and depression-related pain cognitions (the Spielberger S tate-Trait Anxiety Inventory and the Pain Cognitions Questionnaire). The me asurement models of the BDI were tested using LISREL structural equation mo delling and their construct validity examined using partial correlation ana lysis. Method. A total of 173 people attending a multidisciplinary pain clinic and 157 patients attending a facial pain clinic completed self-report measures of pain and mood prior to their respective clinical consultations. Results. The model offered by Novy et al (containing one affective factor ' Negative-attitude suicide' and two somatic factors 'Performance difficulty' and 'Physiological manifestacions') fitted both pain groups better than th e model offered by Williams and Richardson (containing one affective factor 'Self-reproach', one somatic factor 'Somatic disturbance' and one factor w ith a mixture of both affective and somatic items 'Sadness about health'). However, when the factors were allowed to correlate in the latter model, bo th models were broadly equivalent. Conclusions. The two measurement models adequately fitted data in both pain samples when the factors were allowed to intercorrelate in the Williams an d Richardson model. Both the affective scales offered by both models could be used in future research, although the somatic factor offered by the Will iams and Richardson model offered much higher levels of internal reliabilit y than either of those offered in the Novy et al. model. The findings are d iscussed in relation to the issue of depression in chronic pain.