For centuries, people with disabilities were segregated, institutionalized, and hidden away in “asylums,” jails, “poor houses,” and large institutions. The segregated locations and institutional, impersonal approach to care led to abuse, neglect, overcrowding, and unsanitary conditions.

Beginning in the 1960s, the abuses endured by people living in institutional settings came to light and exposés highlighting the abuses were made public. Geraldo Rivera’s groundbreaking expose of Willowbrook State Institution in New York in 1973 was one of the catalysts for law and service reforms – one of the earliest being the Civil Rights of Institutionalized People Act (CRIPA) of 1980 which protected the rights of people in correctional facilities, nursing homes, mental health facilities, and institutions for people with IDD.

The 1980s saw the momentum growing  in terms of recognizing and acknowledging the needs of individuals experiencing co-occurring IDD and mental health disorders.  In 1982, psychologist Steven Reiss first coined the term diagnostic overshadowing – the concept that psychiatric needs of those with IDD were often minimalized or dismissed as part of their disability.

In 1984, NADD presented the first conference in Suffern, NY with 400 people in attendance.   In 1993, the first International NADD conference was held in Boston.  Conferences have been held every year since those first conferences, and the NADD conferences have become a professional home for many.

Throughout the 1990s, people with dual diagnoses were still siloed into either the mental health system or the IDD system.  The systems ran parallel, but separate.  NADD increased efforts to educate both the mental health professionals and IDD professionals in the need for a whole person approach. 

In 1997, NADD Press was formed for the purpose of producing and distributing the most advanced research in this particular field of study.  That same year, Dr. Fletcher began working with industry and clinical experts on the DM-ID (Diagnostic Manual-Intellectual Disabilities), a book to use in concert with the DSM (Diagnostic Statistical Manual) to support more accurate diagnoses and address the challenges in diagnosing people with IDD. The DM-ID was published in 2007 and is now in its second edition DM-ID-2.

In 2007, NADD began working in partnership with the NASDDDS (National Association of State Developmental Disabilities Directors) on the Accreditation and Certification Programs in the IDD/MI Dual Diagnosis Best Practices.  The impetus to develop these credentialing options for professionals was driven by the intention of providing a set of standards to support and raise the professional bar of those working with people experiencing these co-occurring diagnoses.