The language of disability is shifting.  Within Canada, the term “mental retardation” was viewed negatively over the last decades and the terms “developmental disability” and/or “intellectual disability” are now both used.  Often, these terms are used to refer to the diagnosis of mental retardation as defined as an IQ below 70 along with limitations in adaptive functioning and onset before the age of 18 years (DSM-IV - Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision, published by the American Psychiatric Association (APA)).

The prevalance (how many people have a developmental disability at any give time) is between 1 and 3% of the population (Roeleveld, et al, 1997; Ouellette-Kuntz and Paquette, 2001).

The causes of developmental disabilities are varied and remain unknown in a large proportion of cases.  Often the known causes are grouped into two categories:

• Genetic - harmful individual genes and aberrant chromosomes
• Environmental - including physical hazards before, during and after birth, as well as adverse domestic and social circumstances

To a parent, family or caregiver a child is first and foremost an individual human with strengths and abilities.  He or she is a full citizen with rights, who needs a variable amount of “assistance” to achieve full inclusion and engagement in society.

Autism Spectrum Disorder

Autism Spectrum Disorders (ASD) are defined by impairments in social interactions and communication, and the presence of restricted activities and interests.  ASDs include Autistic Disorder and Asperger Disorder.  Symptoms typically appear in early childhood as social-communication difficulties and/or delayed developmental milestones.

There is no clear consensus on the prevalence of ASDs, although research reports rates ranging from 16 to 67 per 10,000 children. 

Autistic Disorder is associated with developmental disability about 70% of the time.  There is an overrepresentation of autism in males with a ratio of 4 to 1 of males to females.  It is now believed that most children with ASD are probably born with it and that a preliminary diagnosis can be made well before the age of three.

Asperger Disorder tends to be diagnosed at a later age than Autistic Disorder.  An individual with Asperger Disorder does not possess a significant delay in language development, however he or she may have difficulty understanding the subtleties used in conversation, such as irony and humour.  Also, while many individuals with Autistic Disorder have a significantly below average IQ, a person with Asperger Disorder possesses average to above average intelligence. 

Dual Diagnosis

Dual Diagnosis refers to individuals who have a diagnosed emotional/psychiatric disturbance as well as a diagnosed developmental disability.  This definition was defined jointly by the Ontario Ministries of Health and Long-Term Care and Community and Social Services in 1997.

In a review of research literature, Reiss (1993) found rates of mental health problems of 15 to 50% in adults with developmental disabilities. 

There is now a clear acknowledgement that children and adults with developmental disabilities can develop the full range of psychiatric illnesses and that they have a higher rate of mental health disorders than the general population.  They are also more likely to be poorer, live in more challenging family circumstances and have fewer friends; all of which are known to be associated with an increased risk of mental health problems (Emerson & Hatton, 2007).  This study described three main reasons which appear to account for the high rates of mental health problems for persons with developmental disabilities:

• The intellectual impairment associated with a developmental disability reduces the child’s capacity for finding creative and adaptive solutions to life’s challenges
• Persons with a developmental disability are at increased risk for exposure to poverty and social disadvantage.  They also have higher rates of stressful life events such as abuse than those without developmental disabilities
• Some particular causes of developmental disability predispose children to particular types of mental health problems

For further information on Developmental Disabilities, Autism Spectrum Disorder and Dual Diagnosis, please refer to the document “Improving Health Outcomes for Children and Youth with Developmental Disabilities.”