The findings of this study have significance for geriatric psychiatry because older adults resist seeking mental health care. Rather, strategies for detecting and treating mental illness in elders are best mounted in other sites in which patients are likely to present in high numbers, including primary care and ASN agencies. Collaborative depression care management models that integrate primary and mental health care have demonstrated effectiveness in improving outcomes of depressed seniors (36
). Because social issues and stressful life events are predominant risk factors for late life depression, and because aging services providers are uniquely qualified to deal with these issues, the ASN is a natural partner with primary and mental health specialty care providers in delivery of care to depressed older adults. While the presence of mental illness among clients of both medical and non-medical home care agency clients is increasingly recognized as a public health problem, with rare exception (38
) aging services agencies and providers of non-medical care management services have not been included in the design of collaborative systems of care for late life depression. Institution of routine screening for depression in the ASN setting is an important step towards further reducing barriers to mental health service delivery experienced by older adults, and to the integration of health and human services in providing their care.
The 26.7% prevalence of major depression in this sample of ASN care management clients is higher than some studies of community-dwelling older adults receiving home care services (17
) and comparable to others (16
). That over one quarter of clients had affective illness reinforces the need for tools with which agency providers can recognize and intervene to assure they receive mental health care. The PHQ-2 and the PHQ-9 both demonstrated good psychometric characteristics for detecting a current major depressive episode in this setting. The longer instrument may be relatively better suited to the ASN agencies though because its greater specificity will result in fewer false positives (non-depressed clients identified as cases) and thus reduce the cost to the agency and its elderly clients of unnecessary interventions.
The findings, however, further indicate that a two-stage process in which only those clients who screen positive on the PHQ-2 (scoring 2 or more) are administered the PHQ-9 performed at least as well, and perhaps better than either alternative; and the PHQ-2/9 would achieve those results with fewer questions than uniform screening with the PHQ-9, saving time and reducing respondent burden. More specifically, 165 of 378 subjects in this sample (43.6%) would have been spared the additional seven PHQ questions by using the PHQ-2/9 approach rather than administering the PHQ-9 to all. Given the average administration time of approximately five minutes for the PHQ-9 in this setting, reducing the screen to two questions (administered typically in a minute or less) would amount to meaningful time savings for the provider and reduce respondent fatigue in the course of a long and comprehensive care management assessment visit. In settings where the prevalence rate of MDE among clients is lower than we observed, of course, the proportion that would be spared the added questions would be higher and the savings in time and effort greater. For busy social service agencies operating on tight budgets while being responsible for addressing multiple, complex social needs of their elderly clients, such efficiencies may tip the balance in favor of adopting a depression screening program.
The tradeoff between using a tool and scoring method leading to a high level of sensitively versus increased specificity is a decision that each agency must make based on its own unique circumstances. This decision would depend on the availability of staff comfortable with the administration and interpretation of the measure, patients’ willingness to be referred, and access to primary care and/or mental health providers. Because screening questionnaires alone have little impact on case detection and treatment outcomes for depression (39
), agencies must have mechanisms in place to assure that further indicated assessment and treatment are available to their depressed clients.
There are limitations that should be considered in interpreting these data. First, we have focused solely on use of the PHQ-9 for detection of major depressive illness in ASN clients. However, because significant stressors are a criterion for entry into the service system, milder or “subsyndromal” depression (SSD) is common in this population also. Most would agree that further evaluation and treatment of those who screen positive for major depression is clinically appropriate, and because SSD has been associated with significant functional morbidity (40
), many would argue that it too should be a target for intervention. However, doing so would greatly increase demands on referral mechanisms; there is a lack of consensus regarding treatment guidelines for SSD; and it remains an empirical question whether the care managers’ social interventions alone are sufficient to resolve the distress of less severely depressed elderly clients. Pending further study of the natural history of subsyndromal depression in clients receiving ASN interventions, we believe that screening and referral should target those with major depression.
Second, because the PHQ-9 was administered during the same interview and by the same interviewer as the diagnostic criterion standard SCID, there is the possibility of interviewer bias. However, it was our interpretation throughout the study that subjects tended to become more comfortable with the interviewer as the assessment progressed, and so tended to under-report their symptoms on the PHQ-9, which was administered early in the interaction. If there were bias associated with this aspect of the study design, it would tend to underestimate the psychometric properties of the screening tool. Also, the three screening approaches tested here were all derived from administration of the PHQ-9 rather than by administering the PHQ-2, PHQ-9, and their combination in unique samples of care management clients. For this reason we could not directly test the time saved by using the PHQ-2/9 instead of routine application of the full PHQ-9 scale. The measures may perform differently when administered by aging service providers than by research personnel, and results found here may not necessarily generalize to other aging services or older adult samples.
This study is the first to examine the criterion validity of the PHQ-2, the PHQ-9, and their sequential administration in aging services clients receiving in-home social work assessments. By developing stronger relationships with primary care and mental health systems, the ASN could help reduce the significant burden of late life mental disorders, and in so doing would also help the ASN achieve its mission of maintaining independence and a higher quality of life for seniors. Use of the PHQ-2/9 in this setting can provide a means of identifying clients with clinically significant depressive disorders, and routing them to care. Future research is needed on the performance of the PHQ-2/9 when administered by ASN staff in the course of routine care management delivery; specific client, social service provider, and agency characteristics that may influence the performance, uptake, and implementation of these instruments; means by which to increase the sensitivity and specificity of depression screening tools, for example through use of more complex scoring algorithms that incorporate other client characteristics; and the best approaches to linking screening to effective treatment of affective illness in ASN clients.