What does the WHOQOL-Bref measure? Measurement overlap between quality of life and depressive symptomatology in chronic somatoform pain disorder.

INTRODUCTION: Quality of life has become an important outcome criterion for psychiatric interventions. Especially in chronic disorders with no complete recovery, the improvement of quality of life is an important treatment goal. Nevertheless, there are methodological problems in assessing quality of life. There is a possible measurement overlap between quality of life and psychopathology, especially depression, which may invalidate research results. This study addresses the quality of life of patients with chronic somatoform pain and its relation to depressive symptoms.
METHOD: One hundred out-patients with somatoform pain disorder at the Behavioural Medicine Pain Clinic in the Department of Psychiatry of the Medical University of Vienna were diagnosed using the SCID for Diagnostic and Statistical Manual of Mental Disorder (DSM-IV). The patients filled out the World Health Organisation Quality of Life Assessment-Bref (WHOQOL-Bref) and the Beck Depression Inventory (BDI). Pain intensity (average pain, maximum pain, minimal pain) and disability (work, leisure and family life) were assessed using visual analogue scales.
RESULTS: Quality of life in somatoform pain disorder was reduced compared to the norm population, especially in the physical and psychological domains. There were highly significant negative correlations between, on the one hand, depressive symptomatology (BDI) and, on the other hand, the physical quality of life domain (r=-0.655, p<0.01), the psychological domain (r=-0.735, p<0.01), the social domain (r=-0.511, p<0.01) and the environmental domain (r=-0.561, p<0.01). In all domains of the WHOQOL-Bref and in the global score, significant differences between the group of patients with severe or very severe depressive symptoms and the group with no or only mild depressive symptoms were found. DISCUSSION: While the WHOQOL-Bref showed a poor quality of life of patients with chronic somatoform pain disorder in general and especially in the physical and in the psychological domains, the high correlation of physical and psychological quality of life scores with depressive symptomatology points to a measurement overlap. It is suggested that assessment of subjective quality of life should always be checked for the influence of depressive symptomatology on the quality of life score.