Introduction

There is a need to improve care at the interface of general medicine and mental health. ¹ Provision of care at this interface is the aim of integrated care. Integrated care occurs when mental health specialty and general medical care providers work together to address both the physical and mental health needs of their patients.

This comprehensive systematic review addresses the evidence for integration of mental health services into primary care settings and primary services into specialty outpatient settings. The research questions were:

1)

What models of integration have been used?

a)

What theoretical models support these programs?

b)

What is the evidence that integrated care leads to better outcomes?

2)

To what extent does the impact of integrated care programs on outcomes vary for different populations (e.g., specific mental illness conditions, chronically ill, racial/ethnic groups, elderly/youth)?

3)

What are the identified barriers to successful integration?

a)

How were barriers overcome?

b)

What are the barriers to sustainability?

4)

To what extent did successful integration programs make use of health information technology (IT)?

5)

What financial and/or reimbursement structure was employed in successful integration programs? Is there evidence to suggest that any specific financial/reimbursement strategy is superior to another?

6)

What are the key elements of programs that have been successfully implemented and sustained in large health systems? To what extent do they follow, or how do they differ from, models that have been studied in published research studies?

The scope of the review included alcohol addiction but not other forms of substance abuse. Inpatient settings are also excluded. The review focuses on four areas: (1) specifying what integration is (and is not); (2) detailing the process through which integrated care may affect clinical outcomes; (3) expanding beyond the scope of prior reviews to include multiple illnesses and patient populations; and (4) specifying the conditions under which various models of integrated care are likely (or unlikely) to work in ‘real-world’ settings. This review also conducted case studies in order to better understand the implementation of integrated care models.

Methods

Randomized controlled trials and high quality quasi-experimental studies conducted in the United States from 1950 to 2007 were reviewed for all questions. Dementia, Alzheimer's, and developmental disorder studies were deemed qualitatively different and were excluded. Descriptive studies were used for the last five questions, including companion articles to included studies; other relevant documents from the grey literature, including websites, conference proceedings, white papers, and governmental reports, were also used to address questions 2, 3, and 5.

The review used both quantitative and qualitative analyses. For quantitative analysis for question 1 we created a taxonomy of integration levels to examine whether integration was associated with improved outcomes. Trials were assigned to one of four levels of provider integration, based on the degree of shared decisionmaking between primary care and mental health providers and whether or not mental health providers were co-located with primary care providers. Simple additive scores were created for integrated process of care based on the presence or absence of ten elements:

• Screening
• Patient education/self-management
• Medication
• Psychotherapy
• Coordinated care
• Clinical monitoring
• Medication adherence
• Standardized followup
• Formal stepped care
• Supervision

The trials were scored and divided into terciles. We also further categorized the trials into an integration matrix based on their provider and process integration levels. We used Forest plots to examine the association of level of integration with patient outcomes for trials of depression care. There were not enough trials of other patient populations for quantitative analysis.

Results for Integrating Mental Health into Primary Care

We identified 33 trials that examined the impact of integrating mental health specialists into primary care. Twenty-six studies addressed depression care and four addressed anxiety disorders. The remaining studies were single studies for somatizing disorders, Attention Deficit and Hyperactivity Disorder (ADHD), and one study addressed both depression and alcohol-related disorders.

Results for Integrating Primary Care into Specialty Mental Health

Only three trials were identified, all of which were covered in a recent systematic review. ¹⁵ The trials used collaborative care models with intermediate to high levels of involvement by primary care providers and regular contact between medical and mental health staff that may, or may not be, co-located.

The trials were consistent in reporting improvements in medical care, quality of care, and patient outcomes. Two programs were found to be cost-neutral as increases in outpatient expenditures were offset by declines in inpatient and emergency room use. ^{16, 17} There was also a significant decline in annual costs for a subsample of patients with substance-related mental and medical comorbidities compared to the control group. ¹⁸ The trials did not report results for serious mental or substance abuse illnesses by age, gender, or ethnicity.

All three trials took place in large, integrated health systems with considerable advantages in co-locating services and shared operational systems. Integration of primary health care into free-standing community substance use disorders treatment clinics with no immediate access to medical health care facilities would likely face additional barriers and challenges not encountered in the trials. Given the minimal cost savings for the subsample of patients with both medical and mental health comorbidities, a sufficiently large caseload to support medical practice may be the most critical concern for providers who are not part of a large system that assesses costs from a health plan perspective.

Case Studies

Thirteen case studies conducted to supplement the traditional systematic literature review help the reader translate the research covered in the comprehensive literature review into actual clinical and administrative practices. A tipping point is being reached as more programs are implemented. Networks of health care organizations developing and implementing various integrated care models are arising as communities of organizations learn together and share information and lessons learned as integrated care gathers momentum.

Discussion

In general, integrated care achieved positive outcomes. However, it is not possible to distinguish the effects of increased attention in general to mental health problems from the effects of specific strategies. The lack of correlation between measures of integration or specific elements of care processes and the various outcomes reinforces the underlying question about the specific effect of integrated care. All but two studies compared integrated care to usual care. The two studies that directly compared two levels of integration, integrated care and enhance referral or consultation-liaison, found no clear differences in outcomes by study end.

It makes sense that introducing a systematic approach and extra attention to treating mental illness in the context of primary health care should yield a beneficial result. There are possible concerns that raising the average level of practice might come at the expense of losing individually expert care. Some might be concerned that the value of introducing a structured approach might prevent some patients from receiving more individualized care. ^{19, 20}

Efforts to implement integrated care will have to contend with the financial barriers posed by fee-for-service payment. Many of the costs involved are not regularly covered by a payment system based on specific in-person encounters. Integration can be fostered by improved health IT but the case for using this approach has not been well documented to date.

Future Research

A major unresolved issue remains to define just what elements of integration are vital in producing the desired goals. Head-to-head trials testing more explicit variation of integration components and elements of care process might help to resolve this issue.

There is considerable work to be done to understand who benefits from integrated care. The effects of comorbidities, both mental and physical, should be included in multivariate models. Eligibility criteria should be broadened to include patients with multiple mental health conditions. More attention should be given to powering studies and collecting data necessary for subgroup analysis for minority groups. Research aimed at efficiently matching clinical and organizational processes and resources to different levels of care for varying levels of severity, and patients stratified by risk and complexity, would build on the efforts the IMPACT trials and Intermountain Healthcare's examples.

Demonstration projects would advance our understanding of the financial structures that best support sustainable integrated programs. The VA's consortium on quality improvement processes is working towards describing best practices adapted to local requirements that facilitate efficient and effective change processes; more work along these lines in a wider range of settings is needed.

More exploration of the business case for integrated care will be needed if plans are ever going to finance such an approach. Programs will be needed to assure that each practice that works with multiple plans is adequately covered to make changing their approach financially feasible. More needs to be done to assess the effect of patient volume and case mix on financial feasibility.

Policy Implications

The big question is whether to view the cup as half full. There is a reasonably strong body of evidence to encourage integrated care, at least for depression. Encouragement can run the gamut from removing obstacles, to creating incentives, to mandating such care. The encouragement will likely differ between fee-for-service care and managed care, although both must address the issues of paying providers. However, without evidence for a clearly superior integrated model, there is a legitimate reason to worry about premature orthodoxy.