1Introduction

Publication Details

Burden of Suffering

Depressive disorders are common, chronic, and costly. Lifetime prevalence levels from community-based surveys range from 4.9% to 17.1%.1-3 In primary care settings, the prevalence of major depression is 6% to 8% (Table 1). 4 Longitudinal studies suggest that about 80% of individuals experiencing a major depressive episode will have at least 1 more episode during their lifetime, with the rate of recurrence even higher if minor or sub-threshold episodes are included. 5 Approximately 12% of patients who experience depression will have a chronic, unremitting course. 5 The substantial public health and economic significance of this chronic illness is reflected by the considerable utilization of health care visits and tremendous monetary costs: $43 billion (1990 dollars) annually, with $17 billion of that resulting from lost work days. 6

Table 1. Prevalence of Depressive Illness.

Table

Table 1. Prevalence of Depressive Illness.

The burden of suffering from depression is substantial. Suicide, the most severe of depressive sequelae, has a rate of approximately 3.5% among all cases with major depression, a risk that increases to approximately 15% in people who have required psychiatric hospitalization. 7 The specific risk for suicide associated with depressive disorders is elevated 12- to 20-fold compared to the general population. 8 The World Health Organization (WHO) identified major depression as the fourth leading cause of worldwide disease burden in 1990, causing more disability than either ischemic heart disease or cerebrovascular disease. Its associated morbidity is expected to increase; unipolar depressive illness is projected to be the second leading cause of disability worldwide in 2020. 9 Furthermore, depression appears to contribute to increased morbidity and mortality from other medical disorders, such as cardiovascular disease. 10

Both the chronicity and recurrence of depressive illness play a large role in depression's heavy disease burden. The more severe a depression becomes and the longer it lasts, the greater the likelihood that the depression will become chronic. 11 Consequently, early effective identification and management of depressive illness will not only decrease the substantial morbidity associated with the current episode but may also decrease the likelihood that the illness will become chronic, with its additional associated morbidity. 12

Epidemiology of Depressive Illness in Adults

Major Depression

Depressive illness can have a variety of presentations, and these range in both severity and chronicity. Major depression is the most severe form; according to criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), it consists of an episode of at least 2 weeks in which an individual has 5 of 9 specific depressive symptoms, 1 of which must be depressed mood or anhedonia (loss of interest or pleasure). 13 These symptoms must cause clinically significant distress or impairment in social, occupational, or other important areas of functioning, a requirement which emphasizes the marked disability resulting from depressive illness. Major depression has a prevalence of 6% to 8% in the primary care setting, making it as common a presentation as hypertension. 4

Dysthymia

Dysthymia, a chronic, low-grade depressive illness of at least 2 years' duration, has a prevalence of 2% to 4% in the primary care setting. 3 Although its symptoms are less severe, the morbidity associated with dysthymia is substantial. 14 The severe impact of the illness is reflected by the 17% of patients with dysthymia who make serious suicide attempts. 15 Furthermore, it is a risk factor for subsequent development of a major depressive episode. 16

Sub-threshold Disorders

Sub-threshold disorders consist of depressive symptoms that are not severe enough to meet DSM-IV criteria but that still cause substantial disability. 13 They are as common as major depression in primary care settings. Presentations may include remitting major depressive episodes, evolving major depressive episodes, or episodes that will never reach criterion for a major depression.

Minor depression, an episodic sub-threshold disorder that is similar to major depression, consists of between 2 and 4 DSM depressive symptoms. It is not an officially recognized DSM-IV diagnosis but is included in DSM-IV as a type of "Depressive Disorder Not Otherwise Specified." 13 Minor depression is at least as common as major depression in primary care sites (point prevalence 8% to 10%). 17 Health-related quality-of-life measures, including physical health, disability, and social functioning, are significantly more impaired for people with minor depression than for people who are not depressed and only slightly better than those with major depression. 18 One-fifth of people with minor depression may progress to major depression within the year. 17

Depression Severity in Primary Care

In general, depressive illness is less severe in primary care than in mental health settings. Patients have fewer psychiatric symptoms, a lower likelihood of a history of major depression, a lower likelihood of having received prior treatment, and a lower risk of psychiatric hospitalization. 19 The short-term prognosis is better, with a greater chance of recovery at 1 year follow-up 19 and a higher rate of response to treatment. 20 Furthermore, this improved prognosis may be independent of adequate treatment for depression. 21

Epidemiology of Depressive Disorders in Children and Adolescents and Special Populations

Depressive disorders are common in childhood and adolescence. The prevalence of major depressive disorder (MDD) is 0.8% in preschool children, 2% in school-age children, and 4.5% in adolescents. 3

Patients with co-occurring depressive and medical illnesses are a key subpopulation as they are at risk of not receiving potentially effective antidepressant therapies. 22 Those with other co-occurring psychiatric illnesses, including substance abuse and anxiety disorders, are at risk for persistent depressive illness. 23 Additionally, differences in depressive illness among different ethnic groups are an important but understudied area. Where the literature provides specific information, we will address the screening and treatment issues for these special populations throughout our review.

Health Care Interventions

Key Role of Primary Care Providers

Primary care practices play a substantial role in the assessment and management of depressive illness. As the initial provider seen by most patients entering the health care system, primary care physicians frequently offer the first opportunity for identification of depressive illness. They also provide the bulk of treatment for depression. People with depressive disorders are more likely to receive treatment from a primary care physician than a mental health professional, 24 and primary care physicians record approximately the same number of yearly patient visits for antidepressant prescriptions as do psychiatrists. 25 However, primary care physicians fail to recognize and treat 30% to 50% of adult depressed patients.26,27 Multiple competing demands, complicated presentations, limited time, and minimal training make identifying and managing depressive illness in a primary care setting a challenging task. 28 Failure to detect depression may be greater for African American or Hispanic patients and for patients under 35 years. 29

Interventions for depression include antidepressant medication, herbal therapies, psychosocial therapies, educational and quality improvement strategies, electroconvulsive therapy, and light therapy. The latter 2 are not first-line primary care treatments and will not be addressed in this review. General categories of therapeutic interventions are listed in Table 2.

Table 2. Treatment Interventions for Patients Identified with Depression in Primary Care.

Table

Table 2. Treatment Interventions for Patients Identified with Depression in Primary Care.

Antidepressant medications include tricyclic antidepressants (TCAs), heterocyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), and other newer agents (such as norepinephrine-serotonin reuptake inhibitors). Alternative herbal therapies, such as St. John's Wort, may also be effective in treating depression, but they are not reviewed here. 30

Psychotherapy is defined as a formal, time-limited communication intervention. Specific forms of psychotherapy that have been studied in primary care populations include cognitive-behavioral therapy and problem-solving therapy. Each of these approaches is based on the theory that distorted thoughts and maladaptive coping strategies lead to depressive illness. Interpersonal therapy (IPT) conceives of depressive illness as an expression of dysfunctional or problematic relationships. Psychotherapies may vary in terms of how formally structured they are, how much contact time is required, and who provides the therapy. Supportive counseling, which may be offered by health care workers with relatively less training and is often based on Rogerian theory, is a less structured form of psychotherapy. Psychoanalytic psychotherapy has not been studied in primary care populations.

Prior Recommendations

In 1996, the U.S. Preventive Services Task Force (USPSTF) found insufficient evidence to recommend for or against routine screening for depression with standardized questionnaires. They recommended that clinicians maintain a high index of suspicion for depressive symptoms in "adolescents and young adults, persons with a family or personal history of depression, those with chronic illnesses, those who perceive or have experienced a recent loss, and those with sleep disorders, chronic pain, or unexplained somatic symptoms." 31 The USPSTF also encouraged physician education in recognition and treatment of depression but did not issue a graded recommendation.

The American College of Physicians (ACP/ASIM) recently released guidelines on the use of pharmacotherapy for depression, but the ACP/ASIM does not have an official policy on routine screening in primary care. 32 The American Academy of Family Physicians also does not have a position on depression screening. Currently, the American Academy of Pediatrics (AAP) has no position statements or guidelines that specifically address the screening, diagnosis, and/or treatment of depression. AAP committees have encouraged pediatricians to include psychosocial questions about the child and family in routine medical interviews and to consider depression in specific groups including children with chronic medical disorders, adolescents considering suicide, victims of violence and natural disasters, and other high-risk groups. Even for these special groups, however, no specific screening instruments are recommended or discussed. In 1994, the Canadian Task Force on the Periodic Health Examination (now the Canadian Task Force on Preventive Health Care) examined the question of screening and recommended against performing routine screening. 33

Analytic Framework and Key Questions

The Research Triangle Institute and University of North Carolina at Chapel Hill Evidence-based Practice Center (RTI-UNC EPC), together with members of the current USPSTF and other clinical and methodologic experts (Appendix A), sought to clarify issues concerning the screening for and treatment of depression by performing a systematic review of the relevant scientific literature on these topics. This systematic evidence review (SER) specifically updates Chapter 49 of the second Guide to Clinical Preventive Services produced in 1996 by the previous USPSTF. 31 A glossary of commonly used abbreviations and acronyms for screening instruments, therapies, and other terms used in this SER can be found in Appendix B.

For prevention to be effective, 3 requirements must be met. First, a reliable and feasible screening process must be available that can accurately identify primary care patients with depression. Second, effective treatment must be available that can improve outcomes for depressed patients. Third, treatment in those detected by screening must improve outcomes compared with usual care in the absence of screening. Our approach to producing this SER on screening for depression takes these 3 issues into account, as discussed with respect to the analytic framework and key questions (below).

Analytic Framework

The analytic framework for this SER is depicted in Figure 1. People with unrecognized depression undergo screening for depression. Screening can correctly classify patients with depression as "depressed" or patients without depression as "not depressed," or it can make false-negative or false-positive mistakes. Patients correctly identified as depressed may then undergo treatment, which may lead to improved scores on depression screening instruments and may also reduce morbidity and mortality, and improve quality of life. Treatment may also have adverse effects, including medication side effects or unnecessary treatment for patients who would have an uncomplicated, nondisabling episode in the absence of treatment. Trials of screening may increase the identification of depression, increase the proportion of depressed people who are treated, or improve indices of depressed mood when compared with usual care.

Figure 1: USPSTF Analytic Framework for Depression.

Figure

Figure 1: USPSTF Analytic Framework for Depression.

Key Questions

Based on the analytic framework, we developed 3 key questions:

  1. What is the accuracy of screening instruments for depression in primary care populations?
  2. Is treatment of depression in primary care patients (with pharmacologic therapy, psychotherapy, combinations of the 2, or educational interventions) effective in improving outcomes?
  3. Is screening more effective than usual care in identifying patients with depression, facilitating treatment of patients with depression, and improving outcomes?

The key questions include the direct effects of screening on detection, treatment, and outcomes (Key Question No. 3) and the 2 main links in the screening "chain" -- namely, the ability of the test to detect depressed patients (Key Question No. 1) and the availability of effective treatment for patients who would be detected by screening (Key Question No. 2). Because our initial survey of the evidence regarding the direct effects of screening suggested that data to answer this question were limited and inconclusive, we decided to examine the evidence for each of the main links in the screening chain as well.

The linkage between studies that examine only diagnostic accuracy and studies that examine only treatment is difficult to study directly because the spectrum of patients included in each type of study may be different. We attempted to examine the evidence for each question that would most likely be generalizable to the patients screened in primary care settings.