Objective: To determine the nature of depressive symptoms in a sample of patients with chronic pain, and to examine the relationship between depressive symptoms and physical disability due to pain.
Design, participants and setting: Cross-sectional study of 812 patients with complete datasets from a total of 2419 patients with pain who were referred to the Pain Management Research Institute at Royal North Shore Hospital, Sydney, between January 2000 and December 2007.
Main outcome measures: Pain severity and distress, physical disability, depressive symptoms, pain self-efficacy, catastrophising, fear of movement/(re)injury, use of unhelpful self-management strategies, sense of control over life, and perceived support from significant others, assessed by the West Haven-Yale Multidimensional Pain Inventory, modified version of the Roland Morris Disability Questionnaire, the depression subscale of the Depression Anxiety Stress Scales, Pain Self-Efficacy Questionnaire, Pain-Related Self-Statements Scale, Tampa Scale of Kinesiophobia, and Pain Self-Management Checklist.
Results: After controlling for the effects of age, sex and duration of pain, depressive symptoms were most strongly correlated with a combination of catastrophising, sense of control over life, physical disability, pain self-efficacy beliefs, higher use of unhelpful self-management strategies and lower perceived social support. Depressive symptoms also correlated with physical disability, but to a lesser extent than other variables, including fear of re-injury, low self-efficacy for activity and pain severity. The depressive symptoms that were rated as most frequently experienced reflected sadness, lack of initiative and lack of ability to experience pleasure.
Conclusions: In patients with chronic pain, depressive symptoms are correlated more strongly with cognitive variables than pain severity and pain distress, while physical disability is correlated more strongly with cognitive, behavioural and pain variables than depressive symptoms. Furthermore, depressive symptoms are characterised predominantly by mood-related symptoms, which suggests differences in the experience of depression in patients with chronic pain compared with those presenting with mental disorders.