Integrated Dual Disorder Treatment

The Integrated Dual Disorder Treatment (IDDT) model is an evidence-based practice that improves quality of life for people with co-occurring severe mental illness and substance use disorders by combining substance abuse services with mental health services. It helps people address both disorders at the same time—in the same service organization by the same team of treatment providers.

IDDT emphasizes that individuals achieve big changes like sobriety, symptom management, and an increase in independent living through a series of small, overlapping, incremental changes that occur over time. Therefore, IDDT takes a stages-of-change approach to treatment, which is individualized to address the unique circumstances of each person’s life.


Integrated Dual Disorder Treatment (IDDT) is multidisciplinary and combines pharmacological (medication), psychological, educational, and social interventions to address the needs of clients and their family members. IDDT also promotes client and family involvement in service delivery, stable housing as a necessary condition for recovery, and employment as an expectation for many.

IDDT Reduces

  • Consumers experience incremental successes through stages of personal change & stages of treatment.

    Relapse of substance abuse and mental illness
  • Hospitalization
  • Arrest
  • Incarceration
  • Duplication of services
  • Service costs
  • Utilization of high-cost services

IDDT Increases

  • Continuity of care
  • Consumer quality-of-life outcomes
  • Stable housing
  • Independent living


Research shows that over 50 percent of people in the United States who have been diagnosed with a severe mental illness will also have a diagnosable co-occurring substance use disorder (alcohol or other drugs) during their lifetimes (see Regier in "Sources" below).

Separate Services

Historically, people with co-occurring disorders have been excluded from mental health treatment because of their substance use disorder. Likewise, they have been excluded from substance abuse treatment because of their severe mental health symptoms. As a result, they frequently have not gotten the help they need.

Negative Life Outcomes

Individuals with co-occurring disorders are more likely to experience the following:

  • Psychiatric episodes
  • Use, abuse, and relapse to alcohol and other drugs
  • Hospitalization and emergency room visits
  • Relationship difficulties
  • Violence
  • Suicide
  • Arrest and incarceration
  • Unemployment
  • Homelessness
  • Poverty
  • Infectious diseases, such as HIV, hepatitis, and sexually transmitted diseases
  • Complications resulting from chronic illnesses such as diabetes and cancer

To address these negative outcomes, IDDT is often integrated with Assertive Community Treatment (ACT). Learn more about integrated IDDT-ACT (click here).


IDDT promotes recovery among people with co-occurring disorders by providing service organizations with specific strategies for delivering services. The implementation of integrated treatment facilitates service system change, organizational change, and clinical change. IDDT is built upon the following core treatment components:

  • Multidisciplinary Team
  • Stage-Wise Interventions (stages of change, stages of treatment)
  • Access to Comprehensive Services (e.g., residential, employment, etc.)
  • Time-Unlimited Services
  • Assertive Outreach
  • Motivational Interventions
  • Substance Abuse Counseling
  • Group Treatment
  • Family Psychoeducation
  • Participation in Alcohol & Drug Self-Help Groups
  • Pharmacological Treatment
  • Interventions to Promote Health
  • Secondary Interventions for Treatment of Non- Responders


There are treatment characteristics (components) and organizational characteristics of the IDDT model that are called fidelity domains. These domains encourage service systems and organizations to develop holistic integrated program structures and treatments. These domains also provide a structure for a continuous quality-improvement process that addresses multiple outcomes.

IDDT facilitates systems change, organizational change, and clinical change when it is implemented with fidelity. Research shows that organizations which maintain fidelity to the original design of IDDT achieve and sustain the best outcomes. IDDT has a fidelity scale that helps organizations implement and sustain the model (see "Related Resources" below).


The Center for Evidence-Based Practices at Case Western Reserve University provides technical-assistance services for IDDT and integrated IDDT-ACT (Assertive Community Treatment) to behavioral healthcare organizations in Ohio through our Coordinating Center of Excellence (CCOE) initiatives, which are supported by the Ohio Department of Mental Health and Addiction Services (OhioMHAS).

More information about the integration of IDDT and ACT (click here)


Recommended IDDT resources produced by our Center:

Organizational Change & Systems Change

Clinical Change

More IDDT resources in our database, including fidelity scales (click here).


Resources from our Center to integrate with IDDT:

Resources from our Center to build dual-diagnosis capacity at organizations:



1.)  Robert E. Drake, Kim T. Mueser, Mary F. Brunette, Gregory J. McHugo (2006). A Review of Treatments for People with Severe Mental Illnesses and Co-Occurring Substance Use Disorders. Psychiatric Rehabilitation Journal, v27, n4 Spring, p360-374.

2.)  Robert E. Drake E., Susan M. Essock, Andrew Shaner, Kate B. Carey, Kenneth Minkoff, Lenore Kola, David Lynde, Fred C. Osher, Robin E. Clark, and Lawrence Rickards (2001). Implementing Dual Diagnosis Services for Clients with Severe Mental Illness. Psychiatric Services, v52, April, p469-476.

3.)  D. A. Regier, M. E. Farmer, D. S. Rae, B. Z. Locke, S. J. Keith, L. L. Judd, and F. K. Goodwin (1990). Comorbidity of Mental Disorders with Alcohol and other Drug Abuse. Results from the Epidemiologic Catchment Area (ECA) Study. Journal of the American Medical Association, v264, n19 November, p2511-2518.


Integrated Dual Disorder Treatment (IDDT), the evidence-based practice, was developed and continues to be studied by researchers at the Dartmouth Psychiatric Research Center of Dartmouth Medical School in Lebanon, New Hampshire. The researchers include Robert E. Drake, MD, PhD; Kim T. Mueser, PhD; and their colleagues.

The Dartmouth PRC has provided leadership for national implementation of IDDT via the Substance Abuse and Mental Health Services Administration. The State of Ohio and the Center for Evidence-Based Practices at Case Western Reserve University—through its Ohio  SAMI Coordinating Center of Excellence (CCOE)—participate in these national initiatives, making significant contributions to the advancement and enhancement of the IDDT model.

Track #6 from our 2008 conversation with IDDT pionoeer Bob Drake, MD, PhD:

IDDT in the Buckeye State (2m 20s)
Ohio has been among the pioneers in IDDT implementation, bringing the model to the Midwest with a blend of pragmatism, hope, and genuine commitment.
Download this audio file (right-click and 'Save As')

Get the entire conversation (click here ).