Intellectual and Developmental Disabilities

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Intellectual and developmental disabilities (IDD) include many conditions that are due to mental and/or physical impairments. These conditions negatively impact intellectual, physical, and/or emotional development. People who have an IDD can experience problems with major life activities such as:

  • Language
  • Movement
  • Learning
  • Self-help
  • Independent living

Across the United States approximately 1% to 3% of the population has an IDD1. Research shows that individuals with IDD experience a higher rate of mental health conditions than the general population. It’s estimated that around 30% of all individuals with IDD will experience a mental health condition at some point in their lifetime2. This awareness is relatively new and mental health conditions in people who have an IDD may go unrecognized or undiagnosed. The most common mental health conditions for individuals with IDD are depression, bipolar disorder, and anxiety, including post-traumatic stress disorder (PTSD).

Individuals with IDD are also more likely to experience trauma (bullying, abuse) and may be more vulnerable and easily hurt by these events because they may not be able to process their thoughts as easily as others, or they may have less access to social support needed to cope with these feelings.

 Common Signs and Symptoms of IDD

  • Delays in or inability to reach milestones in motor development like sitting, crawling, and walking
  • Delays in learning to speak or difficulty with speech or language skills
  • Difficulty with self-care skills
  • Poor problem-solving and planning abilities
  • Behavioral and social problems

With appropriate support and education, the mental health of a person with IDD can be managed.


1. Stromme P, Diseth TH. Prevalence of psychiatric disorders in children with mental retardation: data from a population-based study. Dev Med Child Neurol. 2000;42:266–270.

2. The co-occurrence of mental disorders in children and adolescents with IDD.

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