A comparative study of nonspecific depressive symptoms and minor depression regarding functional impairment and associated characteristics in primary care☆
Introduction
The introduction of operationalized classification systems for mental disorders, such as the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) [1] and the International Statistical Classification of Diseases, 10th Revision [2], has brought about the issue of subthreshold disorders [3]. A person with psychiatric symptoms not reaching the threshold for a formal diagnosis according to the operationalized classification system is regarded as having subthreshold mental disorder. Among others, subthreshold depression has been paid the greatest attention in this field, which led to the definition of numerous subthreshold conditions of depression. The definitions of these various disorders are often based on different numbers of symptoms, duration of symptoms, exclusion criteria, and associated impairment [4]. To standardize research and communication in subthreshold depression, a new provisional subthreshold depression category, minor depression, was introduced for further exploration in the appendix of DSM-IV. Following DSM-IV, minor depression can be diagnosed when an “essential feature” of major depression (dysphoria or anhedonia) is present over a period of 2 weeks with at least 1 but not more than 3 additional symptoms of depression. Judd et al [5] proposed a category not meeting criteria for minor or major depression called “subsyndromal symptomatic depression” (SSD), which is defined as a 2-week period without the essential features but with at least any 2 of the other depressive symptoms.
Depending on the varying definitions, the prevalence of subthreshold depression ranges from 5% to 16% among primary care patients and from 2.2% to 24% in community samples [6], [7], [8]. The clinical relevance of subthreshold depression has been demonstrated in a number of studies. Johnson et al [9], for example, found that patients with subthreshold depression had high rates of service use and medical care costs. Furthermore, these patients had an increased risk for developing severe forms of depressive disorders [10], [11]. Their symptoms were associated with significant levels of functional impairment [5], [12] similar to those of other medical conditions [13]. Although there is evidence that subthreshold depression may have long-term effects on overall health and on medical care costs, Helmchen and Linden [3] have argued that shifting the threshold of defined mental illnesses toward healthy states could lead to a “psychiatrization” of normal life with the negative psychological consequences of stigmatization and an undermining of coping capacities [14]. The lowering of thresholds could also lead to an increase in health care costs and thereby lead to a cutback in resources for patients with serious and life-threatening diseases [15].
The question of valid thresholds separating normal psychological distress from mental illness is related to the dimensional approach of affective disorders. Akiskal et al [16] proposed a dimensional concept for unipolar major depression, reaching from depressive temperament to major depressive episode and from hyperthymic, as well as cyclothymic temperament, to full-blown syndromes of bipolar affective disorders. Without anchoring the depressive spectrum in a personality concept, Angst and Merikangas [17] also proposed a dimensional approach for the classification of depression. The results of their longitudinal study showed little stability for the subtypes of depression, including syndromal and subsyndromal diagnostic categories [18], so that the authors concluded that “depression is better expressed as a spectrum rather than a set of discrete subtypes” [18].
Therefore, this study aimed at evaluating the clinical relevance of subthreshold depression and at finding clues for the nature of the depression concept, taking into account 2 different definitions, minor depression, which is proposed in DSM-IV, and nonspecific depressive symptoms (NDS), introduced by Judd et al [19] as SSD. For the latter, we prefer the label NDS for different reasons: to date, there is no evidence to what extent this condition overlaps with other mental disorders or whether these symptoms are actually specific for depressive syndromes. Also, SSD is frequently used as a synonym for subthreshold depressive syndromes [3], which could confuse the issue.
The study was carried out in the primary care setting because of the aforementioned high prevalence of subthreshold depression in this context and the unresolved question about diagnosing and treating primary care patients with depression. Two aspects of clinical relevance will be considered: functional impairment and associated characteristics (ie, sociodemographic factors such as sex, marital status, employment status). These aspects will be compared between patients with subthreshold conditions, patients with major depression, and nondepressive control patients. In accordance with the spectrum hypotheses of depression, we expected to find differences in risk factors between the 3 diagnostic groups (NDS, minor depression, major depression) and nondepressive patients but no differences between the diagnostic groups themselves. Regarding functional impairment, we presumed pronounced differences between patients with major depression and nondepressive patients. We also expected to find differences between subthreshold patients and nondepressive patients, such as in the previously presented studies.
Section snippets
Data collection and subjects
The study was part of a research project carried out to evaluate a treatment program for patients with subthreshold depressive disorders in primary care. To identify patients having minor depression or related disorders, we asked patients visiting their general practitioner to complete a questionnaire during their waiting time. Of 16 family practices from a small town near Heidelberg, 6 were enlisted in our study. On predetermined days from June to November 2001, a total of 815 patients, 18
Prevalence rates and severity of the depression categories
To examine the point prevalence, the relative frequencies of the aforementioned categories were computed (see Table 1). Using χ2 analysis to test for equal distribution of disorder categories without considering the nondepressive primary care patients, we obtained a significant χ2 value (χ22 = 9.90, P < .01), that is, that the diagnosis of NDS was significantly more frequent than major and minor depression.
In addition to the frequencies, we used the severity index of the respective disorders to
Discussion
The current findings concerning the prevalence rates are in accordance with the results of other studies (eg, [6], [7]). Recently Rucci et al [8] found a weighted prevalence of 9.9% for the subthreshold depressive episode in a community sample. In our study, we found a prevalence rate of 6.2% for the stricter DSM-IV definition of minor depression. However, this rate increased to 15.3% as NDS was included in the definition of subthreshold depression. The prevalence rate of NDS is consistent with
Acknowledgments
The authors thank Andrea Noon who kindly lent her support in translating the manuscript.
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This study was supported by the Medical Faculty of the University of Heidelberg, Heidelberg, Germany (project 2221/2000).