Dysthymia: clinical picture, extent of overlap with chronic fatigue syndrome, neuropharmacological considerations, and new therapeutic vistas

Dysthymia, as defined in the American Psychiatric Association and Internati onal Classification of Mental Disorders, refers to a prevalent form of subt hreshold depressive pathology with gloominess, anhedonia, low drive and ene rgy, low self-esteem and pessimistic outlook. Although comorbidity with pan ic, social phobic, and alcohol use disorders has been described; the most s ignificant association is with major depressive episodes. Family history is loaded with affective, including bipolar, disorders. The latter finding ex plains why dysthymia, especially when onset is in childhood, can lead to hy pomanic switches, both spontaneously and upon pharmacologic challenge in as many as 30%. Indeed, antidepressants from different classes - tricyclic an tidepressants (TCAs), monoamine oxidase inhibitors (MAOIs), reversible inhi bitors of monoamine oxidase A (RIMAs), selective serotonin-reuptake inhibit ors (SSRIs) and, more recently, amisulpride, and spanning noradrenergic, se rotonergic as well as dopaminergic mechanisms of action - have been shown t o be effective against dysthymia in an average of 65% of cases. This is a p romising development because social and characterologic disturbances so per vasive in dysthymia often, though not always, recede with continued pharmac otherapy beyond acute treatment. Despite symptomatic overlap of dysthymia w ith chronic fatigue syndrome - especially with respect to the cluster of sy mptoms consisting of low drive, lethargy, lassitude and poor concentration - neither the psychopathologic status, nor the pharmacologic response profi le of the latter syndrome is presently understood. Chronic fatigue today is where dysthymia was two decades ago. We submit that the basic science - cl inical paradigm that has proven so successful in dysthymia could, before to o long, crack down the conundrum of chronic fatigue as well. At a more prac tical level, we raise the possibility that a subgroup within the chronic fa tigue group represents a variant of dysthymia. (C) 1999 Elsevier Science B. V. All rights reserved.