Depression and pain are both burdensome ailments that affect a major proportion of the population. It is evident that depression and pain frequently coexist, with treatment and outcome implications.

To review the literature on the nature, prevalence and co-morbidity of depression and pain, the biological and psychological mechanisms involved and treatment options, thus presenting a broad overview of the current information available.

Relevant sources were identified from PubMed and Medline databases using a combination of keywords including depression, pain, prevalence, co-morbidity, biological and psychological mechanisms, serotonin (5-HT), norepinephrine (NE), hypothalamic-pituitary-adrenal (HPA) axis, amygdala, functional magnetic resonance imaging (fMRI), antidepressant and psychological therapy.

It is evident from the research that depression and pain are common co-morbidities. Pain as a physical symptom of depression affects approximately 65% of patients, leading to less favourable outcomes and greater health care utilization. Moreover, depression is a common feature in chronic pain patients and can affect pain threshold and tolerance. Evidence from biological and psychological studies has revealed mechanisms that link chronic pain to depression. Several classes of anti-depressants and psychological interventions have been used successfully in the treatment of somatic symptoms of depression and for a variety of pain syndromes.

Pain and depression are linked by overlapping phenomenology, neurobiology and therapy. They are mutually interacting, and the interaction has significant treatment and outcome implications.