Integrating mental health care and primary care has been identified by the World Health Organization as a critical step in addressing the heavy burden of mental health conditions. The New Freedom Commission on Mental Health recommended this approach to care in its 2003 report. More recently, the Affordable Care Act provides incentives for integrating care to improve quality and reduce costs and outlines models for doing so, such as accountable care organizations and patient-centered medical homes. Given the strong push toward integrated and collaborative care, what is the evidence that concomitantly treating mental health and general medical conditions in the primary care setting improves overall health outcomes?

Researchers under contract to the Agency for Healthcare Research and Quality (AHRQ) conducted a comprehensive literature review to answer this question. Early in their search for published studies, they found that only depression had the evidence base to support a comparative effectiveness review. Although anxiety disorders were represented, the available studies did not meet strength-of-evidence criteria. Their findings are reported in a 278-page report recently released by the AHRQ, Practice-Based Interventions Addressing Concomitant Depression and Chronic Medical Conditions in the Primary Care Setting.

Half of all Americans live with a chronic medical condition, according to research cited in the review. About 24 million people (nearly 8% of the U.S. population) have diabetes. Roughly the same number of Americans have chronic obstructive pulmonary disease, and an additional 23 million have asthma. Up to a quarter of people with chronic medical conditions experience limitations in daily activities, and even individuals without such limitations report significant reductions in quality of life for themselves and their families.

Of all mental health conditions, depression contributes the greatest societal burden as measured by social and economic costs. By 2030, depression will be the single leading cause of overall disease burden in high-income countries. In 2000, the economic burden of depressive disorders in the United States was estimated to be $83.1 billion, according to research cited in the report, and more than 30% of these costs was attributable to direct medical care. The prevalence of depression among persons with diabetes ranges from 11% to 31%. Ranges are 13% to 20% for persons with arthritis, 10% to 47% for those who have experienced a heart attack, and 9% to 50% for individuals with cancer.

The AHRQ literature review examined whether collaborative care models can improve either depression outcomes or general medical outcomes—or both—for adults with one or more chronic medical conditions. The review focused on interventions that are “practice based”—that is, those that target the care process within a system of care. Studies that involved medication only, devices, or psychotherapy only were excluded. Examples of practice-based interventions are coordinated care, integrated care, and collaborative care, and these interventions often involve a care manager. The researchers made no attempt to specifically define such interventions. Broadly, such interventions bring together primary care providers and mental health providers to address the comprehensive needs of the patient.

A total of 24 published articles met criteria for the review. They report data from 12 studies—11 conducted in the United States and one in Scotland. Sample sizes ranged from 55 to 1,001, and study duration ranged from six to 60 months. All studies characterized their respective intervention as a form of collaborative care, specifically targeting depression, and compared it with usual or enhanced usual care. Medical conditions included arthritis, cancer, diabetes, heart disease, and HIV, all of which have been shown to be associated with depression.

Meta-analyses conducted for the AHRQ review found moderately strong evidence that intervention recipients experienced greater improvement than comparison patients in depression symptoms, treatment response, remission, and depression-free days. Intervention recipients also reported greater satisfaction with care and better quality of life in the domains of both mental health and general health. Few of the studies reported data on outcomes for chronic medical conditions, except for diabetes. Patients with diabetes who received collaborative care showed no difference in diabetes control (change in HbA1c) compared with patients in control groups.

The review uncovered numerous research gaps. In particular, more research is needed to examine whether effective treatment of depression in primary care can alter the course of chronic disease. Such studies will require larger samples, longer time frames, and joint funding from multiple institutes. In addition, many real-world primary care patients have multiple comorbidities, and “perhaps what the field needs most to understand,” the report notes, “is what models of care work best for patients with common clusters of disease.” Diabetes, hypertension, and obesity, concomitant with depression, is such a cluster. More studies are also needed of collaborative care for primary care patients with other mental disorders, such as anxiety, psychotic disorders, substance use disorders, and cognitive disorders. In addition, the literature review found no studies of colocation of mental health services and no head-to-head trials of various approaches that would enable researchers to identify the active ingredients of specific models.

The literature review is available on the AHRQ Web site at effectivehealthcare.ahrq.gov.