DYSTHYMIA - CLINICAL AND EXTERNAL VALIDITY

This paper reviews current evidence in support of dysthymia as a sub-a ffective disorder that precedes major affective episodes, often by mor e than a decade. In cases beginning in childhood or adolescence, dysth ymia is associated with high familial rates of mood disorders, sad a r ecurrent pattern of superimposed major depression. At least two trait- like markers, sleep electro-encephalographic and thyroid axis abnormal ities - similar to those in major affective disorder - have been repor ted. These data indicate a common pathophysiological substrate for bot h dysthymia and major depressive illness. All classes of antidepressan ts - most recently the serotonin re-uptake and the reversible MAO inhi bitors - have been shown to be effective. Dysthymia was fairly recentl y included in the US(DSM) and WHO(ICD) classifications of mental disor ders, because it characterises a prevalent clinical presentation of de pression in both psychiatric and general medical settings. Patients gi ven this diagnosis, instead of presenting with acute or full-blown epi sodes, often complain of low-grade chronic affective malaise for as lo ng as they remember, yet without clinically observable signs of depres sion. As a result, questions have been raised about its validity, but from fundamentally opposite positions: (i) Is dysthymia better concept ualised as a personality (or neurotic) rather than mood disorder? (ii) Can dysthymia be distinguished from :major depressive illness? This p aper examines these and related questions along both clinical and exte rnal validating strategies, and in particular, the more recent accumul ated evidence in support of the utility of the concept of dysthymia.