A review and synthesis of studies on minor depression and other 'brand names'

Declaration of interest Authors were employees ofthe American Psychiatric Association and no other funds were obtained. The DSM-III (American Psychiamc Association, 1980) system introduced a new paradigm for establishing diagnoses in psychiatry by utilising objective, operationalised criteria with specific thresholds. Greater reliability in diagnosis was achieved, as was improved communication among researchers and clinicians regarding whether an individual had a mental disorder or, in epidemiological terms, was a 'case'. The primary focus of DSM-111 was on populations presenting for treatment in mental health speciality settings. Questions have repeatedly been raised as to whether the specifically delineated disorders in DSM-111, DSM-N (American Psychiamc Association, 1994) and ICD-10 Diagnostic Criteria for Research (DCR) (World Health Organization, 1993) capture the full spectrum of psychopathology in the general population and primary care settings, as well as in the speciality mental health sector (DeCruy & Pincus, 1996). Aware of limitations in coverage, DSM and ICD-10 systems include atypical conditions or those not meeting full criteria for a specific mental disorder in 'not otherwise specified' categories. None the less, there have been continual calls for the addition of other new 'disorders'. During the DSM-N process, over 150 different new disorders were proposed, with varying levels of evidence supporting their addition to the classification (Pincus et al, 1992). We review recent literature on forms of subthreshold or minor depression and examine how they have been defined, the methods used to evaluate and assess these conditions and the results of those studies. Subthreshold depression is particularly important because of the prevalence, clinical significance and cost of these disorders. Studies have demonstrated the potential prevalence of depressive symptoms in various combinations of as much as 24% of the population (Horwarth et al, 1992). Not only are the numbers of individuals with subthreshold depressive syndromes quite large, but the degree of morbidity and functional impairment is also extensive. Wells et a1 (1992) found that while the degree of impairment is somewhat less than that associated with major depression, it is quite comparable to that of other medical conditions (DeGruy & Pincus, 1996). In addition, individuals who do not meet the full criteria for major depressive disorder manifest high rates of service utilisation and medical care costs (Johnson et al, 1992). Finally, the characterisation of minor forms of depression provides an opportunity to identify individuals potentially at risk for more severe forms of the disorder and to develop interventions that might prevent more extensive morbidity. These conditions have not been a major focus within the speciality mental health community because most individuals with these conditions present to primary care providers, or seek no treatment, rather than seeing speciality mental health clinicians. In fact, a continuing problem in the relationship between primary care and speciality mental health care is that each group is often looking at different parts of the 'elephant' of mental morbidity. Primary care physicians see much more in the way of subthreshold conditions, whereas speciality physicians see the more severe end of the spectrum. Some attempts to break down these barriers have been developed, such as the DSM-N Primary Care Version (American Psychiamc Association, 1996) and the ICD-10 Chapter V Primary Care Version (World Health Organization, 1996). However, both primary care versions are based on the DSM-N and the ICD-10 DCR, respectively, and do not fully capture all the issues that are important in primary care, including the focus on subthreshold conditions. An increased focus in this area may help to link better the primary care and mental health communities in research and clinical care.