How Do We Understand Depression in People with Persistent Pain?

Depression and depressed mood are common in people with persistent (chronic) pain, exacerbating disability and worsening quality of life. Yet the relationship between persistent pain and depression remains unclear, despite its importance for designing or adapting interventions to address both pain and depression. Meta-analysis of cognitive and behavioral interventions designed for rehabilitation of persistent pain shows small benefits for distress. However, substantial variation between studies in patients’ baseline levels of depression and in quality of treatments militates against any clear conclusions. Apart from these interventions, longitudinal studies on chronic pain and depression in adults from clinical populations provide weak evidence that depression worsens pain outcomes. We systematically searched for and reviewed 14 longitudinal studies that explored the association between persistent pain and depression, aiming to identify: (1) the effects on pain of baseline depression; (2) the effects on depression of baseline pain; and (3) possible mediating variables, with particular attention to methodology. Unfortunately, most studies used unsuitable instruments to measure depression, and we could draw only tentative conclusions about effects over time. Better models and clearer measurement strategies are required for a next generation of clinically useful treatment trials and, meanwhile, some implications for treatment are explored.