Pain and depression are often associated. The frequency of pain complaints in depressed patients is 13-100%. In general, depressed patients have a higher pain threshold than do controls, but lower and unchanged thresholds have also been observed. The frequency of depression in chronic pain patients is 1.5-100%. Pain etiology, short education, marital status, gender, psychiatric family history and unemployment are risk factors for depression. Possible mechanisms underlying the pathophysiology of depression and pain could be involvement of the monoamines (5-HT and NA) and the HPA axis.