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Thursday, May 5, 2011

Physical pain and depression
Major depression is a triad of psychological, somatic and physical symptoms. Over 75% of depressed patients report painful physical symptoms involving the neck, back, head, stomach and the skeletomuscular system. Not only can chronic pain lead to depression, but also vice versa. Fibromyalgia, accounting for 2–4% of the general population, is a common cause of chronic pain. It has been estimated that 20–40% of such patients have co-morbid depression with a lifetime prevalence of about 70%. This raises the question whether there is a common mechanism linking pain and depression. Neuroanatomically both the locus coeruleus and the raphe´ nuclei project to the spinal cord where they gate sensory pathways from the skeletomuscular areas. As there is evidence that both noradrenaline and 5-HT are dysfunctional in depression, it is perhaps not surprising to find that the pain threshold is often reduced in patients with depression. Conversely, different types of antidepressants have been shown to have an antinociceptive effect in both rodent models of neuropathic pain, and clinically in fibromyalgia, chronic fatigue syndrome, postherpetic neuralgia and diabetic neuropathy. In general, it would appear that the dual action antidepressants (such as the TCAs and SNRIs) are more effective than the SSRIs.

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