Comparing mental illness and intellectual and developmental disabilities
August 2, 2016
When I first started working for Thompson Policy Institute, I lacked an understanding of the nuances between different types of disabilities. Without even realizing it, I had lumped together very different conditions into similar categories and after doing some reading, I see why I was confused! The classification between intellectual and developmental disabilities (IDD) and mental illnesses (MI) can be blurry. Intellectual and developmental disabilities can co-occur simultaneously with mental illness, so drawing distinctions can be a challenge. Nevertheless, this post will serve to provide some clarity between the different types of intellectual and developmental disabilities and mental illnesses people live with everyday.
According to the US Center for Disease Control and Prevention (CDC), “developmental disabilities are a group of conditions due to an impairment in physical, learning, language or behavior areas.” Developmental disabilities include specific conditions like autism spectrum disorder (ASD), vision impairment, ADHD, cerebral palsy and hearing loss. Some developmental disabilities begin before birth but all occur during the developmental period and continue throughout the person’s life. Developmental disabilities can be either physical or intellectual in nature, so some extra clarification is used around cognitive-specific intellectual disabilities.
Intellectual disabilities fall under the umbrella category of developmental disabilities and together they are abbreviated as IDD’s. Intellectual disabilities are disabilities specific to cognitive processes, while developmental disabilities can be cognitive, physical or even both. According to the AAIDD, intellectual disabilities are classified by “significant limitations in intellectual functioning, significant limitations in adaptive behavior, and onset before the age of 18.” Disability professionals often work with people who have both physical and intellectual impairments so it’s important to consider how the two impairments impact each other.
There are 200 forms of mental illnesses, but some most are familiar with include clinical depression, bipolar disorder and anxiety disorders. Mental Illness (MI) impacts the way an individual handles his/her daily life demands because it alters and disturbs his/her typical thought processes on a continuum from slight to severe. Mental illnesses are treatable and about 1 in 5 adults in the US experience a mental illness in any given year. IDD’s and mental illness can occur simultaneously and these specific cases occur in about 1/3 of the total population receiving state disability care nationwide.
While intellectual and developmental disabilities (IDD’s) can slow cognitive ability among other processes, mental illnesses alter cognitive perception without diminishing cognitive ability. Both have impact on the brain and neurological functions, but it is a distinction that helps clarify the confusion between the two.
Written by Evan DeVries for Thompson Policy Institute