Double depression: A distinctive subtype of unipolar depression

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Abstract

Whether depression is a single disease that varies from mild to severe, with varying episode durations and difficult course patterns, or whether it is an umbrella diagnosis representing depressive subtypes with different psychological and biological characteristics has been debated by clinicians and researchers for many years. However, most scientists now agree that understanding the heterogeneous subtypes of depression allows for greater accuracy in describing and differentiating patients suffering from depression and, therefore, greater precision in describing the most efficacious treatment plan. This article will focus on the distinctions between unipolar major depression, double depression and dysthymia, and will review the history of the DSM classifications for these “subtypes” of depression. The paper will also discuss the fact that despite a lack of scientific validation of the subtypes of major depressive disorder, clinicians and researchers continue to subclassify major depression and, particularly, for the purpose of testing the efficacy of new psychopharmocologic and psychosocial treatments. There continues to be a need for future research to more clearly establish the predictive value in terms of course, recovery, rates of relapse and treatment in regard to distinguishing type of depression as well as to validate the current nosology.

Introduction

Whether depression is a single disease that varies from mild to severe, with varying episode durations and different course patterns, or whether it is an umbrella diagnosis representing depressive subtypes with different psychological and biological characteristics has been debated by clinicians and researchers for many years. However, most scientists now agree that understanding the heterogeneous subtypes of depression allows for greater accuracy in describing and differentiating patients suffering from depression and, therefore, greater precision in prescribing the most efficacious treatment plan.

DSM-IV (American Psychiatric Association, 1994) is the most recent DSM edition used as a diagnostic guideline. Each successive edition of the DSM has been based on research studies which have added data on the validity and reliability of categorizing and diagnosing depressive disorders. Before the publication of DSM-III in 1980, chronic depression was classified as a personality disorder rather than an affective disorder, and it was not until 1987 with the publication of DSM-III-R that chronic major depression existed as a formal diagnostic category (McCullough et al., 1996).

According to the DSM-IV, the essence of major depressive disorder “is a clinical course that is characterized by one or more major depressive episodes without a history of manic, mixed or hypomanic episodes”. Dysthymia is described as “a chronically depressed mood that occurs for most of the day, more days than not, for at least 2 years” (1 year in children). Double depression can be diagnosed if, after the initial 2 years of dysthymia, a person then suffers from major depressive episodes, which are considered superimposed on the dysthymic disorder. When a person no longer meets the criteria for a major depressive episode but the dysthymic symptoms persist, that person would be diagnosed as having dysthymic disorder only (American Psychiatric Association, 1994). Validity and reliability concerns regarding chronic depression were addressed again by the DSM-IV Unipolar Mood Disorders Field Trial in preparation for the publication of DSM-IV. One of the results of the work done in the Field Trial was the addition of longitudinal course specifiers of major depression to the DSM-IV appendix (American Psychiatric Association, 1994). These course specifiers will be discussed in another section of this paper.

This paper will focus on the distinctions between unipolar major depression, double depression and dysthymia, and will review the history of the DSM classifications for these “subtypes” of depression. The paper will also discuss the fact that, despite a lack of scientific validation of the subtypes of major depressive disorder, clinicians and researchers continue to subclassify major depression and, particularly, for the purpose of testing the efficacy of new psychopharmacologic and psychosocial treatments.

Section snippets

Major depression

The National Comorbidity Survey (NCS) reports a 17.1% lifetime prevalence for a major depressive episode in the general population (Kessler et al., 1994). For an appropriate diagnosis of a major depressive (MD) episode according to the DSM-IV, a person must have 5 of 9 symptoms during the same 2-week period. Of the following 9 symptoms, a diagnosis of MD must also include either the first or second symptom: 1) depressed mood; 2) loss of interest or pleasure; 3) significant weight loss or gain,

Dysthymia

The NIMH Epidemiological Catchment Area (ECA) Study reported rates of dysthymia, based on random population samples at three sites, ranging from 2.1% to 3.8% (Robins et al., 1984). The National Comorbidity Survey (NCS) showed a 6.4% lifetime prevalence rate for dysthymia (combined rate for men – 4.8% and women – 8.0%) (Kessler et al., 1994). Another epidemiological study of dysthymia in the general population found a lifetime prevalence rate of 4.7% in a survey of 511 subjects (Weissman and

Depressive personality disorder

There is disagreement in the field regarding dysthymia and personality disorders. Some scientists believe that most chronic, early-onset, low-grade depressions should be thought of as personality disorders rather than primary affective disorders.

Conceptions of chronic depressive disturbances have evolved over the decades from “Depressive Temperament” – 1920s, to “Depressive Psychopathy” – 1950s, to “Hysteroid Dysphoria” – 1960s, to the more recent “Borderline Subaffective Type” – 1980s which

Relationship between major depression and dysthymia

To address the issue of whether or not people with major depression have a different profile of depressive symptoms than those people with dysthymia, a study was done using DSM-IV Mood Disorders Field Trial data (Klein et al., 1996). Two subgroups were selected from the Field Trial: 39 subjects with dysthymia and no history of major depression and 62 subjects with recurrent major depression who had full recovery between episodes and who have no dysthymia. The two groups differed significantly

Double depression

According to the DSM-IV, if a person has had dysthymia for 2 years and then has major depressive episodes, in addition to the underlying dysthymic disorder, “double depression” is diagnosed. When that person returns to a “dysthymic baseline” and no longer meets criteria for MDD, only dysthymic disorder is diagnosed (American Psychiatric Association, 1994). Double depression is distinguished from partially reduced major depression because DD requires preexisting dysthymia.

Findings from the CDS

Summary

Depression is a chronic and serious illness. A review of the literature on the course and outcome of affective disorders showed that 15% of patients with a severe major depression of more than one month's duration, who were hospitalized at least once for depression, died of suicide (Guze and Robins, 1970, Robins and Kulbok, 1988). People who suffer from double depression have a longer duration of depression, higher rates of relapse and recurrence than those with major depression alone (Keller

Conclusion

On the basis of current data, it is not possible to definitively answer the question of whether double depression is best characterized as a subtype of major depression. For purposes of diagnostic clarity, treatment research and clinical prognosis, the differences described in this paper suggest that a separate classification of double depression from major depressive disorder is still warranted.

Several points critical to diagnosing depressive disorders seem to be clear from the studies that

Discussion of “Double Depression: A Distinctive Subtype of Unipolar Depression” led by Daniel G. Blazer, M.D. from Duke University

It is important to recognize that all of these discussions are made possible by the operationalized criteria derived from the Washington University criteria, the Research Diagnostic Criteria, and later, the DSM criteria. It is also important to maintain skepticism regarding these criteria and carefully consider whether the data better support being a “splitter” or a “lumper”. We are currently overrun with data and need to look at the same data in a very different way.

Our diagnostic system is

General discussion

  • Dr. Paykel – What was the overlap between depressive personality and dysthymia?

  • Dr. Hirschfeld – In three or four data sets, there is about 50% overlap between them.

  • Dr. Clayton – Were there gender differences in depressive personality?

  • Dr. Hirschfeld – they were about the same as for MDD.

  • Dr. Rush – Consistent with your data, we have shown chronic depression and acute depression to be equally responsive to treatment.

  • Dr. Fawcett – Do you have data regarding impairment?

  • Dr. Blazer – Our data indicate

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