Neuroinflammatory mechanisms linking pain and depression

Depression and chronic pain have been estimated to co-occur in up to 80% of patients suffering from these disorders, with this co-morbidity being more disabling and more expensive to both patients and society than either disorder alone. A number of neural substrates have been proposed to underlie this association; however, there has been increased interest and support for a role of neuroimmune and neuroinflammatory mechanisms as key players in this dyad. This chapter will provide an overview of the clinical and preclinical data supporting a role for neuroimmune alterations in depression-pain co-morbidity. We propose that such changes may impact on the functioning of key brain regions modulating emotional and nociceptive processing, thus resulting in the behavioural, psychological and physical symptoms observed in patients exhibiting depression and co-morbid pain.