Intellectual Disabilities and Related Disorders

Intellectual disabilities (ID) is defined by three identifying factors: below average intellectual functioning (IQ below 70 or equivalent); deficits in adaptive daily functioning; and the onset of the disability prior to the age of 18 years (Fletcher et al, 2007, DM-ID).  The DSM IV diagnoses of Borderline Intellectual Functioning and Mental Retardation are usually used.  These conditions often coexist with other disabilities, developmental or otherwise, such as Autism, Pervasive Developmental Disorder, Traumatic Brain Injury, Genetic Syndromes such as Fragile X Syndrome and Prader Willi Syndrome, Chromosomal Disorders such as Down’s Syndrome, and birth or early trauma such as Cerebral Palsy and Shaken Baby Syndrome.

Many of the symptoms presented by this population are behavioral and are repeatedly attributed to their developmental challenges or their intellectual disability.  However, it has become increasingly clear that people with intellectual and developmental disabilities are at risk for mental illness in the same way as the general population.  In fact, some estimates indicate that people with these disabilities are up to four times more likely to develop a mental illness (Fletcher et al, 2007, DM-ID).  This might be due to more limited coping skills, increased vulnerability to abuse, neglect, and sexual exploitation, and social isolation due to limited supports for accessing the community or poor communication skills.  The challenge is, for caregivers and the mental health professional, trying to understand the unique way in which mental health symptoms might be expressed in a person with disabilities.  For instance, a person with limited communications skills might “drop to the floor” or become “aggressive” at the prospect of going to a social activity.  The person may in fact have social anxiety, but this presents itself as non-compliant or aggressive.  This is not to say that the behavior is not just a poor coping mechanism; however, in the attempt to discover why the behavior exists, mental health issues (for example, anxiety) ought to be explored.

Research literature on the diagnosis and treatment of mental illness in people with intellectual and developmental disabilities is limited.  However, progress in the research is being made.  The National Association for the Dually Diagnosed (NADD) continues to make strides in this area and has published the DM-ID (Diagnostic Manual for People with Intellectual Disabilities) as an important work on this topic.

RELATED LINKS

1. The National Association for the Dually Diagnosed - NADD
   
2. The American Association of Intellectual and Developmental Disabilities - AAIDD
   
3. Definition of Intellectual Disabilities - The American Association of Intellectual and Developmental Disabilities