The occurrence of depression with physical symptoms and pain is common. On the other hand, comorbid depression is also common in chronic pain syndromes. Antidepressants are effective in the treatment of psychological and physical symptoms of depression and chronic pain symptoms of non-depressed patients.
It is not well described how antidepressants relieve the pain. However, it is suggested that this effect is related to serotonin and noradrenaline. Analgesic effects of antidepressants are independent from their effects on the mood. Antidepressants which have effects on both serotonin and noradrenaline are more effective than those with effects on one of these neurotransmitters in the treatment of depression and comorbid pain syndromes. Tricylic antidepressants (TCAs) have serotoninergic and noradrenergic effects. Therefore, they are superior to monoaminergic antidepressants, such as SSRIs, with regard to analgesic and antidepressant effects. The usage of TCAs is limited because of their safety profile and side effects. SNRIs have similar analgesic effects to TCAs. On the other hand they have lower side effects and a better safety profile. Additionally, SNRIs are more effective than SSRIs in the treatment of physical pain syndromes. SNRIs have a similar safety profile to SSRIs and almost similar costs to the older agents.
Better diagnosis and treatment of pain symptoms, which are strong indicator of depressive relapses, will provide better quality of life and productivity in patients with depressive disorders.