Understanding Dual Diagnosis


For the purpose of this web resource, the term “dual diagnosis” refers to individuals who are diagnosed with both a mental illness and an intellectual or developmental disability. These individuals often present with complex issues that are not readily addressed by providers or treatment designed to meet the needs of either mental health or intellectual/developmental disability. However, these individuals have a great need for supports, treatments, resources, and approaches that are highly integrated and collaborative across various disciplines to effectively support the whole person. To help you understand this subset of the individuals we serve and their specific needs, here are some resources:

The National Association for the Dually Diagnosed (NADD)
NADD is a not-for-profit membership association established for professionals, care providers and families to promote understanding of and services for individuals who have developmental disabilities and mental health needs.

National Alliance on Mental Illness (NAMI)
Mental Health Conditions - This website gives an overview of specific mental illnesses, treatment, and support.

National Association for the Dually Diagnosed (NADD) - Ontario Chapter
Dual Diagnosis: An Introduction to the Mental Health Needs of Persons with Developmental Disabilities - A book which can be viewed and printed by chapter or ordered from NADD

National Core Indicators
2011 Data Brief – Dual Diagnoses - The 2008-2009 National Core Indicators Consumer Survey Report provides descriptive and outcome data on 11,569 adults (18 years and older) receiving publicly financed developmental disabilities services in 26 states and four sub-states entities. This Data Brief explores characteristics and responses of individuals who had dual diagnoses of intellectual disability (ID) and mental illness and contrasts them with characteristics and responses of individuals who had a diagnosis of ID only.

Strategies for Supporting People with Co-Occurring Mental Illness and Intellectual Developmental Disabilities
National Association of State Directors of Developmental Disabilities Services, Charles R. Moseley, Ed.D., 2012, “Presentation given at SAMHSA's Olmstead Policy Academy in 2012 providing a review of state challenges and strategies for supporting people with co-occurring intellectual and developmental disabilities and mental illness”


Dual Diagnosis: The Long Way Home
A Canadian Broadcasting Corporation (CBC) documentary about an Ontario couple whose son suffers from dual diagnosis. Click on the link below and search “dual diagnosis”.

Smiley, E., Cooper, S., Finlayson, J., Jackson, A., Allan, L., Mantry, D., McGrother, C., McConnachie, A., & Morrison, J. Incidence and predictors of mental ill-health in adults with intellectual disabilities: Prospective study. The British Journal of Psychiatry Sep 2007, 191 (4) 313-319; DOI: 10.1192/bjp.bp.106.031104

Lauren Charlot & Joan B. Beasley (2013) Intellectual Disabilities and Mental Health: United States–Based Research, Journal of Mental Health Research in Intellectual Disabilities, 6:2, 74-105

Understanding Intellectual Disability and Health
University of Hertfordshire/Hertfordshire Partnership University Foundation Trust & St George’s, University of London 

Dual Diagnosis: A guidebook for caregivers
This guidebook gives caregivers the tools they need to understand how mental illness might look in a person with a developmental disability, and information on what to do and where to go for help. It was written in order to help caregivers to collaborate with health care providers.

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