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What are intellectual and developmental disabilities?

Intellectual and developmental disabilities (IDD) are a category of disabilities that are present at birth or develop before a person becomes an adult. People living with an IDD may or may not have lifelong challenges with learning and independent living.

Intellectual and developmental disabilities are large umbrella terms covering many other disabilities. Many of these disabilities and conditions have a spectrum of traits and symptoms. They impact each person differently, even if they share a diagnosis.

People with IDD may take longer to learn to speak and take care of their personal needs, such as dressing or eating. A person with an IDD may require some level of support for their entire life. This will look different for everyone. Don’t assume that you will be able to tell a person has an IDD just by looking at them or talking to them.

There are more than 200 known causes of intellectual and developmental disabilities.

Common examples of these kinds of disabilities are:

Down Syndrome is a genetic condition that occurs when someone is born with a full or partial extra copy of chromosome 21 in their DNA.
Fragile X Syndrome is another genetic condition caused by a mutation (a change in the DNA structure) in the X chromosome.
Fetal Alcohol Spectrum Disorder (FASD) refers to several conditions that can occur if a child is exposed to alcohol during pregnancy.
Autism Spectrum Disorder (ASD) is a spectrum of conditions that affect how people interact with others, communicate, learn, and behave.

Person-First and Identity-First Language

Person-First Language

People with disabilities are, first and foremost, people. The person is not defined by their disability; they have a disability. Often, person-first language is preferred in the IDD community. When you address someone with an IDD or their family members, this means putting the person before the disability; you would say a person with a disability rather than a disabled person.

Identity-First Language

People in the Autistic and Deaf community often prefer identity-first language, meaning you would say “Autistic adults” rather than “adults with Autism.” People usually use identity-first language because they feel that their disability is an important part of their identity.

According to the Board of Health for Public Health Sudbury & Districts, Canadian organizations “have used person-first language to discuss disabilities since the 1980s.” Ensuring that language referring to people with disabilities is respectful.

When you are discussing a person's disability, you must consider their preferences. It is always best to ask if you are unsure what a person would prefer.

Community Support

According to the Centre for Addiction and Mental Health (CAMH), people diagnosed with intellectual and developmental disabilities (IDD) often have complex healthcare needs. People with these disabilities are more likely to be also diagnosed with mental health disorders than people without these disabilities.

People diagnosed with “IDD have a long history of stigma and discrimination related to their disability.” In the past, you had very few options if you or a family member were diagnosed to have an IDD. Children diagnosed with certain IDDs were often sent away to an institution for life if their support needs were too high or hidden at home as a family secret. There is also a long history of negative language, even by medical professionals, and poor treatment.

In Ontario, children and adults with IDD are included and supported in our communities. You or your family members can attend local schools and daycares and get jobs. Many people with these disabilities live on their own or in group homes. You may receive different levels of support from families, friends, and community programs.

Community agencies support people with IDD at every stage of their lives, from childhood to senior years. They provide essential services so you or your family member living with an IDD can attend school, find meaningful employment, and participate in activities.

You can find a community agency in your area by contacting 211 Ontario or visiting our mapping tool, Services Near Me, for programs and services in your area.

For More Information

Community Living Ontario - A provincial association that promotes citizenship, belonging, and equality of people who have an intellectual disability. The website has contact information and links to Community Living centres across Ontario.
ConnectAbility - An interactive website with information for those working with people with intellectual disabilities. The library section has information in many languages.
Ontario Disability Support Program - This website has links to information about the Ontario government's financial, employment, residential and family support programs.
MyDirectPlan (MDP) - An online tool for managing Special Services at Home (SSAH), Passport, and Residential funding.
MyJobMatch - Supported employment process that connects job seekers with a disability, employment support professionals, and employers.