Practical Geriatrics: Clinically Significant Nonmajor Geriatric Depression

Depression in later life has serious health consequences, including an elevated risk of mortality due to suicide and medical illness and amplification of disability associated with medical and cognitive disorders (1). Geriatric depression often leads to increased health care costs (1). Although major depression is the most studied and well-defined depressive syndrome, other depressive subsyndromal disorders are also associated with significant functional impairment and disability (2,3).

In this column we focus on clinically significant geriatric depression that does not meet established criteria for major depressive disorder. This category encompasses several clinical subtypes with subtle distinctions. We highlight the phenomenologic and therapeutic evidence in support of this category of disorders.

Nosologic and diagnostic complexities

In current psychiatric practice and research in both elderly and nonelderly adult populations, two principal approaches define depression: depressive symptoms, and more specific depressive illnesses or disorders defined in terms of the duration, number, and type of depressive symptoms. Most nonpsychiatrists typically regard depression in terms of the first construct, whereas psychiatrists use the second construct. Most studies demonstrate that patients with depressive symptoms, even in the absence of a specific depressive disorder, experience considerable morbidity and reduced social functioning (4,5).

Subsyndromal depressive spectrum

Subsyndromal depressive-spectrum disorders have been proposed by various investigators in their conduct of longitudinal studies of large populations of adult and geriatric patients. In a 15-year follow-up community-based cohort-study, Angst and colleagues (4) studied the longitudinal course of young adult patients with a diagnosis of major depressive disorder, dysthymia, recurrent brief depression, or minor depression. These researchers found very little stability for the specific types of depression among persons who continued to manifest depression during the follow-up period: 51 percent of patients with major depressive disorder and 44 percent of those with recurrent brief depression met criteria for another subtype of depression (4).

When stability was observed, the same subtype occurred in combination with the development of another subtype. Among patients with a single subtype, severity was greatest among those with dysthymia, whereas patients with combined subtypes had greater severity than those with a single subtype. The researchers suggested that symptom threshold and recurrence—but not the minimum duration of depressive episodes—should serve as a basis for classification (4).

Does nonmajor depression among elderly persons differ from depression among younger adults? Some similarities and differences exist in the phenomenology and disease course of depression between elderly and younger adults. Blazer and colleagues (6) identified a symptom-cluster profile unique to people older than 60 years, characterized by depressed mood, psychomotor retardation, poor concentration, constipation, and poor self-perception of health. This cluster was associated with cognitive deficits and physical illness and did not correspond to any particular DSM category.

The spectrum of geriatric depression also extends to patients with underlying medical or progressive dementing disorders who may develop depression during their illness (3). Among bereaved individuals, subsyndromal and minor depression stood between major depression and absence of depression in terms of their effect on the overall adjustment to widowhood, which supports the spectrum concept (7). Some investigators have identified clinical features of dysthymia that are clearly different among elderly persons, including late onset, comorbid medical illness, cognitive deterioration, and frequent adverse life events (8).

Epidemiology and clinical features

The nosologic status of minor depression together with the variability in diagnostic criteria contributes to the variability in prevalence estimates of these disorders. Relevant factors include differences in diagnostic systems, severity threshold, and duration of illness required for the diagnosis of various affective states or disorders. Despite these methodologic considerations, there is broad consensus on the prevalence and clinical impact of nonmajor forms of mood disorders both in the broader community and in more specialized clinical settings (6).

Community samples

Minor depression and other nonmajor forms of clinical depression are more prevalent in adult and elderly populations than is major depressive disorder. Tannock and Katona (2) suggested that depressive symptoms or subsyndromal cases of minor depression are common among elderly persons. Blazer and Williams (5) found that 14.7 percent of a community sample of persons older than 65 had "substantial depressive symptoms." Despite methodologic differences, there is emerging consensus that the prevalence of minor depression changes with age: symptoms increase among people in their 30s, decrease in middle age, increase steadily in old age, and increase very steeply among people older than 80 years. This phenomenon appears to be unrelated to higher rates of mortality, somatization, and institutionalization among depressed elderly persons. It has also been suggested that severe depression is mitigated with age (9).

Long-term-care settings

The prevalence of minor depression has been estimated in special populations and settings. For example, minor depression affects up to 50 percent of residents in long-term-care facilities and up to 25 percent of patients in primary care settings (1). In all settings, the prevalence of depressive symptoms is two- to fourfold higher than the prevalence of major depression (9). Among institutionalized elderly persons, up to 70 percent reported feeling "depressed, sad, or blue" at least enough to cause minor problems in their day-to-day activities (9).

Medical settings

Most patients with mental illness are seen exclusively in primary care settings. Primary care has thus been the focus of recent studies of minor depression (10). It is estimated that 3 to 16 percent of medical outpatients suffer from minor depression. Up to 64 percent of medical outpatients complain of depressed mood. Studies of depression among persons with medical illnesses usually report the negative impact of depression on the rates and speed of recovery as well as the overall impact of depression on disability and health care costs (9,10).

Degenerative and neurologic disorders

Many diseases of the central nervous system are associated with an elevated prevalence of depression. Mood disturbances are common among persons with neurodegenerative disorders, including probable Alzheimer's disease and Parkinson's disease, and after ischemic injury to the brain (poststroke depression). However, depression is not invariably seen with all degenerative disorders, and the prevalence and profile of mood and behavioral aberrations are relatively disease specific (11,12). These findings suggest that specific neurobiologic mechanisms and pathways may be responsible for mood disorders across conditions.

Among persons with Alzheimer's disease, both major depressive disorder and other clinically significant forms of depression that do not meet the threshold for major depression have been described. Prevalence estimates of depression among persons with Alzheimer's disease vary widely, from zero to 86 percent. Estimates of depression among patients with Parkinson's disease also vary widely. Studies that have used more stringent criteria for the diagnosis of depression suggest that the true prevalence of depression among persons with Parkinson's disease may be 20 to 40 percent. Approximately half these patients would meet criteria for major depressive disorder, and the remainder exhibit features consistent with minor depression and dysthymia (12).

Differences in diagnostic instruments and in the clinical methods used to diagnose depression—patient interviews as opposed to caregiver reports—probably contribute to these discrepant finding. The overlap in clinical features between Alzheimer's disease, Parkinson's disease, and affective disorders also complicates the diagnosis of depression among patients with these disorders. The prevalence of depression is low among patients with frontotemporal dementia and progressive supranuclear palsy, which indicates that mood disturbances are not a natural consequence of all forms of neurodegeneration (11).

Depression after vascular injury to the cerebral hemispheres is now a well-recognized clinical entity. Poststroke depression may present as minor or major depression and can occur within 12 to 24 months after the incident. Major as well as less-severe forms of depression occur among patients with neurodegenerative and vascular disease, which suggests that these forms of depression may represent a clinical continuum rather than distinct clinical entities (13).

Treatment

Studies of treatment of nonmajor depressive disorders are limited (14,15). Little is known about treatment strategies for clinically significant nonmajor depression. Most studies have focused on dysthymia and minor depression in primary care settings.

Descriptive studies have established that primary care providers use one or more of three modalities in treating depression: watchful waiting, medication, and referral to the specialty sector. In the case of watchful waiting, the most commonly used modality, it has been shown that return visits involve sympathetic listening and a show of interest, and in some cases brief "common sense" counseling.

The use of medication is virtually the only active treatment delivered by primary care providers, but the evidence of efficacy of psychopharmacologic interventions for persons with nonmajor depression is lacking. Oxman and Sengupta (14) reviewed treatment of minor depression and concluded that older persons were as responsive to treatment as younger persons. The limited evidence from randomized trials that have included a control condition suggests that antidepressants and counseling have some benefit and should be attempted. However, the placebo responses were high in the few controlled studies that have been conducted, and such nonspecific therapeutic factors as an attentive physician may be particularly beneficial.

Conclusions

Both similarities and differences exist in the clinical manifestations of clinically significant depressive disorders. There is an emerging consensus from epidemiologic and longitudinal studies that supports the idea of a continuum of depressive disorders, ranging from the very mild "subthreshold" depression to major unipolar and bipolar disorders. All forms of clinically significant depression are associated with considerable economic and psychosocial consequences. Current approaches to studying affective illness that adhere to traditional nosologic categories may not be adequate for the next generation of research into the biologic and psychosocial correlates of this group of disorders. We propose clinical criteria for the diagnosis of clinically significant nonmajor depression among elderly persons (see box). These criteria are consistent with operational definitions of minor depression used in other clinical studies but are broader in clinical and methodologic scope.

Acknowledgments

This work was supported in part by a Young Investigator Award from the National Alliance for Research on Schizophrenia and Depression and by grant K23-MH-01948 to Dr. Lavretsky and grants MH-55115, MH-61567, and KO2-MH-02043 to Dr. Kumar from the National Institutes of Health.

The authors are affiliated with the department of psychiatry and biobehavioral sciences of the University of California, Los Angeles, School of Medicine. Send correspondence to Dr. Lavretsky at UCLA Neuropsychiatric Institute, Room 37-425, 760 Westwood Plaza, Los Angeles, California 90095 (e-mail, [email protected]). Marion Z. Goldstein, M.D., is editor of this column.