Delineating psychopathologic clusters within dysthymia: a study of 512 out-patients without major depression.

Background: The literature indicates that emotional-cognitive symptoms are much more characteristic of dysthymia than the vegetative and psychomotor symptoms of major depression, yet this is insufficiently emphasized in the official criteria listed in the criteria of the American Psychiatric Association. Furthermore, as previous studies have examined these symptoms more in relation to prevalence than to possible symptom aggregation, in the present analyses we address both aspects.

Methods: In two multicenter collaborative trials, 512 out-patients meeting the symptom criteria of DSM-III-R dysthymia but without major depression were recruited. In this respect they conformed to the conceptual framework of ICD-10 which tends to restrict dysthymia to a subthreshold depression without excursion into severe depressive episodes. The Montgomery Asberg Depression Rating Scale (MADRS) and the Hamilton Anxiety Rating Scale (HAM-A) were used to assess depressive and anxiety symptoms.

Results: Symptoms most frequently observed, besides depressed mood (100% by definition), were 'low energy or fatigue' (96%) and 'poor concentration or indecisiveness' (88%), followed by 'low self-esteem' (80%), 'insomnia or hypersomnia' (77%), 'poor appetite or overeating' (69%) and 'feeling of hopelessness' (42%). Interestingly, in the subjects with fewer than five symptoms, the most frequent were low energy or fatigue (93%), poor concentration or indecisiveness (79%) and low self-esteem (77%), the other symptoms being present in no more than half the sample. MADRS factor analysis identified two main factors: the first consisting of apparent and reported sadness, and the second concentration difficulties and lassitude. HAM-A factor analysis identified two factors clearly differentiating somatic and psychic symptoms.

Limitations: Because suicidal patients were excluded on the ground of human subject concerns, our sample is representative of the milder range of symptomatology within the spectrum of dysthymia. This may in part explain the low prevalence of neurovegetative symptoms.

Conclusion: Despite this, the present study involves the largest sample of pure dysthymia ever studied. Our results indicate that dysthymic disorder appears to primarily involve psychologic symptoms. The psychological symptoms themselves seem to cluster into sadness versus mental fatigue; as for anxiety symptoms, they appear divisible into somatic and psychic clusters, with the latter prevailing in dysthymia. Dysthymia proper, dominated by negative affectivity, might be distinguishable from a 'neurasthenic' subform dominated by low energy or 'deficit' symptoms at mental and physical levels.