Minor and Subsyndromal Depression: Functional Disability Worth Treating

Mood disorders are among the most prevalent illnesses encountered by primary care physicians (PCPs) and are associated with many unexplained physical symptoms, high rates of health services utilization, and significant functional disability.1,2 Unfortunately, they often go unrecognized and untreated by PCPs, who are a key entry point to health care for older adults and who treat most of the individuals with depressive symptoms.3,4 To date, most clinical research on mood disorders has focused on major depression. Widespread dissemination of the latest research findings by the media has heightened public awareness of major depression as a serious public health problem. Perhaps as a result, it has reduced the reluctance of clinicians to prescribe antidepressant treatments while increasing the likelihood of patients to accept treatment, as judged by a boom in the sales of various antidepressant medications in recent years. In contrast, the minor, dysthymic, and subsyndromal forms of depression, in which symptoms are of insufficient duration, intensity, or number to meet formal criteria for a major mood disorder, have garnered far less research and media attention. Moreover, efforts to identify primary care patients for the presence of a mood disorder and then provide feedback and treatment advice to clinicians in order to improve the quality of health services delivery have tended to focus on major depression and to ignore other mood disorders. In recent years, a growing body of evidence has developed that indicates that dysthymia, minor depression, and subsyndromal depression are associated with a considerable decrement in functional disability that is comparable to that of major depression.1,5,6 The report by Lyness and colleagues in this issue of JAGS extends our understanding of the prevalence of clinically significant depressive symptoms and associated functional disability to older adults receiving primary care services.7 They found a 15.1% prevalence of either minor (5.2%) or subsyndromal depression (9.9%) and a 6.5% prevalence of major depression among 224 patients aged 60 years or older who were screened for the presence of a mood disorder shortly after presenting for primary care services. Not surprisingly, patients with major, minor, or subsyndromal depression had significantly greater levels of depressive symptoms, functional disability, and cognitive impairment compared with nondepressed individuals. However, after adjustment for age, gender, educational level, and clinic site, older adults with either minor or subsyndromal depression had a level of cognitive impairment and functional disability similar to those who met formal criteria for a current episode of major depression. Furthermore, the investigators could not attribute these similarities to the burden of medical illness between groups or to the presence of another Axis I disorder. These data suggest that PCPs should be concerned not only about recognizing patients with major depression but those with minor depression and subsyndromal depressive illnesses as well. Unfortunately, various pharmacologic and counseling strategies proven effective at treating major depression have had little impact on these other depressive conditions.8,9 Lyness et al. also provide additional evidence that clinicians frequently fail to distinguish between the various mood disorders, even when they do recognize that their patient is experiencing symptoms of emotional disturbance. Indeed, almost half of the older adults identified as experiencing mild forms of depressive illness received antidepressant medications whereas more than half of those who met formal criteria for a current episode of major depression did not. Thus, there remains a need for quality initiatives to improve both the quality and the appropriateness of the depression care provided to older adults by PCPs. Various studies have calculated the prevalence of minor, dysthymic, and subsyndromal mood disorders at between 8 and 27% in both community and primary care samples. This estimate is two to six times greater than the prevalence of major depression within these same settings.5,7,9,10 Given the persistence of depressive symptoms in more than 50% of untreated patients at 1-year follow-up,9 minor depressive syndromes may, in fact, generate a substantially larger attributable burden of functional impairment in the US than major depression. Nevertheless, whether subsyndromal depression remains a “wastebasket” term or identifies a group of patients whose symptoms are associated with poorer functional status remains to be determined. See also p 647 Questions also remain about whether and how PCPs should inform, work-up, or treat primary care patients experiencing milder forms of depression. Clinical trials are, therefore, needed to test strategies generalizable to non-research settings that are capable of effectively treating subsyndromal and minor depression among older adults. Such studies should include sufficient sample sizes of diagnostically heterogenous older adult patients to detect clinically meaningful, as well as statistically significant, differences in patient outcomes in order to guide policy makers, clinicians, and patients.11 Resources and clinical studies should initially be targeted at older patients who are at highest risk of experiencing adverse health and functional outcomes from mood disorders.12,13 Until efficacy studies can be completed to determine the best strategies for treating older adults who have substantial levels of depressive symptoms but who do not have major depression, how should PCPs manage the care of these patients? Given clinicians'notoriously poor recognition of their patients'mental distress, use of a self-administered case-finding instrument such as the Patient Questionnaire (PQ) portion of the PRIME-MD (mood disorder sensitivity 62% and positive predictive value 80%)10 or depression screening scales such as the CES-D14 may facilitate early case identification and allow for more efficient allocation of treatment resources. Data from the Medical Outcomes Study suggest that as many as 25% of patients with subsyndromal depression will develop major depression within a 2-year period.15 Therefore, patients reporting more than occasional symptoms of late-life depression require at least regular follow-up visits to monitor for the development of more major conditions. Absence of a formal mood disorder diagnosis does not preclude symptom-specific treatment based on clinical judgment and clinical experience. The use of antidepressant agents, such as selective serotonin reuptake inhibitors with a favorable risk-benefit profile for use in older patients as well as psychosocial interventions, may be beneficial in select patients. Finally, given the weight of evidence that has conclusively demonstrated the ineffectiveness of PCPs at recognizing and treating major depression without additional diagnostic and treatment resources, we must expect that any improvements in the quality of primary care and subsequent patient outcomes for the so-called minor mood disorders among older adults will only be achieved at the cost of added direct healthcare expenditures.16