Intellectual and developmental disabilities (IDDs) are a group of disabilities that begin at birth or in childhood that can affect a person’s intellectual, physical and emotional development. People with IDDs can have problems with both intellectual functioning and adaptive behaviors, which are everyday life skills like self-care, communication and social interaction.

People can have mild, moderate or severe IDDs. The most common causes are genetics, problems during pregnancy or childbirth, and childhood illness – but the cause of IDD is unknown in most cases.

IDD is a term that encompasses a variety of diagnoses. While some IDDs have physical signs and symptoms, others can be invisible to the eye. Some of the most common ones are:

  • Autism spectrum disorder
  • Down syndrome
  • Fetal alcohol spectrum disorder
  • Fragile X syndrome

IDDs can happen in any family. There are no racial, educational, social or economic boundaries when it comes to IDDs. An estimated 6.5 million Americans have an intellectual or developmental disability, and approximately 1-3 percent of the global population is affected – or as many as 200 million people.
People with IDDs are like everyone else – they have unique interests, values and personalities. They cherish their family and friends, and they are capable of contributing to the community.

The abilities of people with IDDs can vary greatly. About 85 percent of people with IDDs have a mild form and can succeed in school and work. However, in more severe cases, they may only be able to communicate on a basic level.

Language is an important part of acceptance and understanding. Experts in the IDD community have outlined terminology that ensures people with IDDs are treated with individuality and dignity. Some of the best practices include:

  • Use “people-first language.” This means you refer to a person with IDD rather than an “intellectually disabled person.”
  • Avoid saying a person is “suffering from,” “a victim of” or “afflicted with” an IDD.
  • Avoid the word “unfortunate” when referring to a person with IDD.
  • When discussing IDDs, people without one are referred to as “typical,” rather than normal.


How Can I Connect?

People with IDDs can form strong personal connections like anyone else, but many people feel nervous about or don’t know how to approach them. When you do take the time to connect with a person with IDD, you’ll likely have a rewarding experience.

If you’re ready to connect with people with IDDs, read our Approachability fact sheet for tips on how to start a conversation, and check out the IDD nonprofits in our area.