Autism and Intellectual Disability

Lynn: When did the Diagnostic and Statistical Manual ( DSM) classification change from Mental Retardation (MR) to Intellectual Disability (ID) and why?

Dr. Gerdts: The official DSM classification changed from MR to ID in 2013 when the DSM-5 came out, along with the change to use “Autism Spectrum Disorder” instead of Autistic Disorder, Asperger’s Disorder, and PDD-NOS. Prior to this official DSM change, a federal statute in the United States called “Rosa’s Law” (named after a young girl with Down syndrome) mandated the replacement of the term MR with ID in 2010. The DSM was updated to be consistent with the new name. Official diagnostic terms describing people with Intellectual Disability have changed over the years and undoubtedly ID will be replaced with another term in the future at some point.

Lynn: Why do some providers still use the MR term?

Dr. Gerdts: Just like any other change, it takes some time to get used to new terminology. For example, as I said above, we the public changed over to ID from MR before the DSM-5 was published when Rosa’s Law was passed in 2010 (and even earlier than this for many in the community). So the community was talking about “ID” instead of “MR,” and research journals were using the term ID well before our DSM manual caught up. We as providers would say the term “Intellectual Disability” with families but then have to write “Mental Retardation” in reports and for billing purposes because the DSM hadn’t shifted over yet. I think people and systems just take some time to catch up.

Lynn: How is ID defined?

Dr. Gerdts: Intellectual Disability is defined as difficulty with aspects of mental capacities such as understanding, reasoning, abstract thought, and problem-solving. It might impact someone’s ability to use language effectively and could cause him/her to have at least some trouble learning or difficulty with academic subjects. It’s kind of like the brain runs at a different horsepower—the brain most definitely still works and still makes connections, but perhaps at a slower pace or in different ways than people who don’t have ID.

In order to be officially diagnosed with ID, some level of intellectual deficit must been documented by IQ testing. However, nowadays, we think about the severity of ID not in terms of precise IQ score, but actually as relating to adaptive functioning—that is, how well people can take care of themselves (or said differently, how much support they require to succeed in everyday life). So once intellectual deficits are established from IQ testing, the person’s level of adaptive functioning determines whether their severity level would be considered mild, moderate, severe, or profound.

Lynn: How common is ID in people with ASD?

Dr. Gerdts: The short answer is that it is quite common. But this is a tough question to answer because estimates have been somewhat different each time we have tried to ask this question, depending on how the study was done and in what city/state/country the study took place. One study found that in 2000-2010, approximately 40% of children with ASD with IQ testing also had ID. Estimates were upwards of 60-70% of people with ASD prior to this time. Estimates of ID in people with ASD have decreased over the years and many children who may have originally been diagnosed with ID are now diagnosed with ASD (so, this isn’t an ­increase in ASD rates but rather a re-categorization of children). Either way, the majority of children with both ID and ASD have mild ID versus moderate, severe, or profound.

Lynn: Why do some with ASD also have ID? Do we know?

Dr. Gerdts: We don’t have an answer for everyone, but at least some of the reason lies in genetics. We are learning more and more about the genetic influences in ASD. Early on, we knew that Fragile X syndrome (a genetic condition affecting the X chromosome) caused some level of ID and could also cause ASD. Now we know that children with ASD who do not have any identified genetic abnormality have higher intellectual ability levels than those who are found to have genetic mutations. Recent findings have shown that mutations to certain single genes that stop them from working the way that they should can give rise to ASD plus ID. But it really seems to depend on the specific gene because mutations to other genes may give rise only to ASD but not ID. We don’t fully understand how or why this comes to be at this time.

Another hint that genetics comes into play in having ASD plus ID versus ASD alone is that the ratio of males to females (which is definitely genetically determined) changes in children with ASD depending on intellectual functioning level. In those with ASD who also have moderate-to-severe ID, the sex ratio is 2:1 males to females compared to 4:1 in ASD in general, and closer to 7:1 in children with ASD without any ID.

There are also certain other risks for ID in general that are important to mention, including problems during pregnancy, during birth, or after certain childhood illnesses.

Lynn: How does having ID impact a person with ASD? Is there any research on this subset of people with ASD that tells us anything significant that might be helpful for families?

Dr. Gerdts: It might mean that additional supports should be put into place to help support his or her independence (e.g., assistance with hygiene habits, food preparation, going to the bathroom). Progress and learning might be a little slower and require more effort than for children with ASD who do not have ID. It might also mean that additional support at school and/or work could be beneficial. For children, this might mean a full or partial day in a specialized resource room at school where academics can be better individualized to the student than a general education classroom or where certain activities of daily living can be emphasized. At work, this might mean a job coach that accompanies an adult with ASD and ID at work. In any case, it’s often helpful for the families of children with ID and ASD to access government support agencies for possible financial assistance, respite care, and/or to discuss housing options in the future.

Lynn: Does having ID change the type of treatments that might be effective for people with ASD?

Dr. Gerdts: I suppose the answer to whether having ID changes the type of treatment your child should receive is yes and no. No because the same general types of therapies and interventions are helpful for many children with ASD regardless of whether they have ID or not, and yes because the specific goals and perhaps modes of intervening may be different. It’s important to emphasize that it’s best to meet with your treatment team to decide what interventions and strategies are appropriate for your child and his/her particular strengths and weaknesses.

In general, young children with ASD and ID will still benefit from early intervention that could include behavioral intervention, speech/language therapy, physical therapy, occupational therapy, and pre-academic supports. Older children with ASD and ID will still benefit from some sort of special education services in school that could include similar therapies as what I just mentioned and individualized academic programming or perhaps life skills intervention.

Children with ASD and ID still benefit from Applied Behavioral Analysis (ABA), which is the most effective intervention for children with ASD regardless of whether they have ID or not. But perhaps goals of ABA for a child with ASD and ID would be different (e.g., focusing on teaching a child without language to use a sound to make a request versus a goal of making a social comment for a child who can speak in sentences). Another example might be speech-language therapy, which is helpful for children with ASD both with and without ID. But perhaps speech and language therapy focusing on conversation skills is not going to be appropriate for a child with limited language whereas a focus on developing and implementing alternative and augmentative communication strategies (e.g., PECS, apps on an iPad to help communicate, signs) could be quite helpful.

Lynn: What do you think of the terms “high functioning” and “low functioning”? Are they used to indicate ID?

Dr. Gerdts: High functioning and low functioning are not official diagnostic terms. There are not now and have never been in the DSM to describe ASD. However, people often use the term “High Functioning Autism” as if it means a certain something about the child. Maybe to some people it means they have language, or that they don’t engage in repetitive hand flapping, or that they have at least one friend. The problem is that level of functioning means different things to different people. Perhaps a child with ASD who doesn’t use much language and has moderate ID is quite flexible, affectionate, and gentle, versus a child with ASD who has a superior level of IQ, but has extreme difficulty with change and is unable to leave the house due to severe tantrums. Who is low functioning and who is high functioning? It goes back to the old saying that if you have met one child with autism, you have met one child with autism. Each child and family is unique in their particular strengths and weaknesses and using overarching terms like “high functioning” and “low functioning” to describe them is often not helpful, or even descriptive.

Lynn: Is there anything else that might be helpful for readers to know about ID?

Dr. Gerdts: An ID diagnosis does not mean that a child will never be able to learn or develop. While a person with ID will likely need some level of support, he or she can most definitely learn new things and take on new independent life skills. Some parents become worried that children are never going to learn how to do certain things, but many children with ID end up surprising parents and providers with what they are able to accomplish.

We’d like to thank Dr. Gerdts for taking time to help us to understand Intellectual Disability.