The Collaborative Care Model (CoCM) originated from a series of research projects led by Wayne Katon at the University of Washington in the mid-to-late 1990s. These culminated in the transformative Improving Mood-Promoting Access to Collaborative Treatment (IMPACT) trial. IMPACT was the largest randomized controlled trial to examine the effects of CoCM from a variety of angles, including depression symptoms, suicidal ideation, physical functioning, quality of life, and cost-effectiveness.
The results showed CoCM’s groundbreaking potential: compared to usual care, Collaborative Care more than doubled the effectiveness of depression treatment. This held true even when “usual care” included a master’s-level behavioral health provider in the primary care clinic delivering specialty behavioral health treatment through a co-located model. From the beginning, it was clear that there is much more to CoCM than simply inserting a behavioral health provider into the primary care setting.
A Landmark Trial
Led by Dr. Jürgen Unützer, the IMPACT study followed 1,801 older adults with depression over two years. Researchers recruited participants from 18 diverse primary care clinics across the United States, representing health organizations in Washington, California, Texas, Indiana, and North Carolina. These clinics ranged from Health Maintenance Organizations (HMOs) and Independent Provider Associations (IPAs) to inner-city public health facilities and Veterans Administration clinics.
Researchers divided patients into two groups. One group received the usual care available at their clinic, which generally involved medication and/or referrals to specialty mental health services, while the other received care under the IMPACT model (now known as Collaborative Care). The team also developed a patient registry for the IMPACT portion of the trial. This registry tracked and measured patient goals and clinical outcomes, facilitating treatment adjustments when a patient was not improving as expected.
Transformative Results
Published in JAMA in 2002, the findings were remarkable. At 12 months, nearly half of the patients receiving Collaborative Care reported at least a 50% reduction in depressive symptoms, compared to just 19% of those receiving usual care. Beyond immediate improvements, the study revealed long-lasting benefits: over two years, IMPACT patients experienced more than 100 additional depression-free days compared to those in usual care. These results solidified Collaborative Care’s status as a game-changing model in behavioral health treatment.
A detailed handout comparing usual care versus IMPACT care provides additional insights into these significant findings.
From the IMPACT Study to Global Implementation
Following publication of the IMPACT trial results in JAMA, healthcare organizations began reaching out to Dr. Unützer for guidance on implementing Collaborative Care. This demand led to the founding of the AIMS Center in 2004.
Since the initial trial, the Collaborative Care Model (CoCM) has been studied in over 90 randomized controlled trials in the United States and abroad. The evidence base consistently shows better clinical outcomes, greater patient and provider satisfaction, improved functioning, and lower health care costs. With such strong results, CoCM has been adopted by more than 1,000 organizations worldwide.
By fostering collaborative, team-based approaches across diverse settings, CoCM has reshaped health care delivery. Today, it continues to improve patient outcomes while reducing systemic costs. Its effectiveness extends beyond depression care: CoCM has proven to work across a variety of disorders—including anxiety, post-traumatic stress disorder, and some substance use disorders—and across a diversity of populations and clinical settings—from pediatrics to older adults and from family medicine to oncology and women’s health.
The model has also been shown to counteract racial and ethnic health disparities in physical and behavioral health outcomes. Many factors likely influence this; to name a few, CoCM reduces stigma around mental health, increases access to high-quality care, and brings non-medication treatments into the medical setting.
Today, Collaborative Care continues to evolve, expanding its reach and adapting to new challenges in behavioral health care across diverse healthcare environments.