Idiopathic pain and depression.

This report summarizes research on the hypothesis that idiopathic chronic pain syndromes and depressive disorders share certain common pathogenetic mechanisms. There is increasing evidence that this may be partly true. Not only do chronic pain syndromes respond to treatment with antidepressants, but there are also striking clinical similarities between these syndromes and depressive syndromes. However, important differences do exist (e.g., the courses of these disorders are usually dissimilar). Family studies show that affective disorders are common in first-degree relatives of patients with idiopathic pain syndromes, but it is impossible to conclude from this that clear-cut genetic factors are of importance. Factors common to both syndromes include common personality traits, shortened rapid eye movements in sleep EEG, hypercortisolaemia and pathological dexamethasone suppression tests, low levels of melatonin in serum and urine and high levels of endorphins and Fraction I in cerebro-spinal fluid. One important common pathogenetic mechanism seems to be disturbances in the serotoninergic system.