A consensus conference on the reasons for the undertreatment of depression was organized by the National Depressive and Manic Depressive Association (NDMDA) on January 17–18,1996. The target audience included health policymakers, clinicians, patients and their families, and the public at large. Six key questions were addressed: (1) Is depression undertreated in the community and in the clinic? (2) What is the economic cost to society of depression? (3) What have been the efforts in the past to redress undertreatment and how successful have they been? (4) What are the reasons for the gap between our knowledge of the diagnosis and treatment of depression and actual treatment received in this country? (5) What can we do to narrow this gap? (6) What can we do immediately to narrow this gap?

The separation of persistent depression into meaningful and useful subcategories, including major depression, dysthymia, recurrent brief depression, and depressive personality disorder, is the subject of much debate. Depressions can be grouped on the basis of their type and severity of symptoms, aetiology, clinical course, or their association with other psychiatric illnesses. Several investigators have conducted epidemiologic and family studies to evaluate the prevalence of depressive disorders, their diagnostic stability over time, and the amount of overlap among the disorders. Although progress has been made toward a better understanding of the different disorders, insufficient evidence exists to support the hypothesis that these disorders are separate and distinct from one another. However, preliminary data suggest that depressive personality disorder is separate from the other disorders. Additionally, several questions have been raised, particularly the extent to which differentiation between the depressive disorders, specifically major depression and dysthymia, has an impact on treatment decisions.

The internal construct validity of the endogenous sub-type of major depression was investigated by statistically modelling the RDC endogenous and DSM-III melancholia diagnostic criteria. Data consisted of symptom ratings on 788 patients with major depression from NIMH Collaborative Depression Study. Results indicated that the symptoms in the criteria do not specify a dichotomous classification, melancholic-non-melancholic or endogenous-nonendogenous. Results did support the existence of two sub-typings, one related to anhedonia, and one related to vegetative symptoms. The vegetative sub-type rarely occurred in non-anhedonic patients. Previous studies may have found support for a simple endogenous sub-type because of this hierarchical relationship and as a result of methodological differences.

The validity of the concept of situational (i.e. reactive) depression as distinct from other major depressive subtypes is examined in terms of psychosocial stressors, personality features, current symptomatology, and clinical course and follow-up. Thirty-eight patients with a recent onset of situational major depressive disorder (i.e. the disorder developed after an event or in a situation the diagnostician deemed likely to have contributed to the episode at that time) were compared with 68 non-situational major depressive patients. These patients were participants in the clinical studies of the NIMH-Clinical Research Branch Collaborative Program on the Psychobiology of Depression. No significant differences between the two groups were found in the total number, content areas, or other categorizations of life events, experienced prior to onset. Some statistically significant differences in current symptomatology and in clinical course and follow-up measures were obtained, but there were none in personality traits. Implications of these results in relation to previously published reports are discussed and caution is recommended in the use of the term situational depression until more definitive data become available.