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Differential Diagnoses and Comorbid Conditions

While there is much more information available about autism spectrum disorder (ASD) than ever before, it can still be a complicated and confusing task to obtain a diagnosis for your child. There is information for parents and pediatricians about early warning signs that indicate the need for further diagnosis. However, depending on a family’s access to a qualified diagnostician, there may be significant differences in how quickly a child obtains a correct diagnosis. This is further complicated by differential diagnoses and comorbid conditions. To help guide you in this process, we provide the following background information about disorders that are similar to ASD (differential diagnoses) and disorders that may occur along with ASD (comorbid conditions).

Differential Diagnoses
Some disorders share common characteristics with ASD. For example, children with ASD can have behavioral concerns, attention and concentration difficulties, mood dysregulation, and medical involvement. All of these symptoms alter with age. It’s not easy to diagnose these children or adolescents because these symptoms may or may not be a result of the ASD. An ASD diagnosis must be differentiated from other disorders that are similar to ASD. When psychologists or psychiatrists make these decisions, it’s called a differential diagnosis.

Comorbid Diagnoses
Some disorders may occur simultaneously with ASD. In these cases, it’s appropriate for children to be diagnosed with ASD and with an additional disorder. When psychologists or psychiatrists make these decisions, the additional diagnosis is called a comorbid condition. The exact prevalence of comorbid conditions in ASD is currently unknown, but studies have estimated from 11 to 72 percent of individuals with ASD have at least one comorbid psychiatric disorder.

To confuse the matter further, some disorders may appear as a differential diagnosis for one child and as a comorbid condition in another child.

For example, consider a young boy who has the following challenges at school:

Has social problems with other students

Seems to violate social rules with adults, like talking when the teacher is talking

Tends to look away from tasks that are presented to him

Throws tantrums when things do not seem to go his way

Misunderstands comments made by others

Can’t seem to sit still


Children with ASD may show significant symptoms of anxiety. Here are some facts about anxiety and ASD:

Eleven to 84 percent of individuals with ASD may also show symptoms of anxiety.

People with ASD may experience symptoms of anxiety regardless of their cognitive functioning.

Children with autism are more likely to show problem behaviors related to anxiety than their typically developing peers.

The symptoms of anxiety are similar in children with ASD (from preschool through young adulthood) and their typically developing peers. In both groups, younger children are more likely to have specific phobias, and older children/adolescents are more likely to have obsessive-compulsive disorder and social phobias.

Because of social difficulties and a potential increased awareness that they’re “different,” many children with ASD have a difficult time with the transition from childhood to adolescence. This could lead to more problems with anxiety, depression, and possibly hostility towards others.

Obsessive-Compulsive Disorder (OCD)
OCD is a disorder that involves obsessive thoughts about a particular subject, activity, or object. A person with OCD engages in compulsive behaviors to eliminate the anxiety caused by the obsessive thoughts. Some common examples of these behaviors are hand-washing or other hygiene activities. For example, a child may wash her hands to prevent contamination or contact with germs. There is often a fear that failing to wash hands will result in illness.

When trying to differentiate between symptoms of OCD and ASD in children, there are some important facts to consider:

Children with OCD have more cleaning, checking, and counting behaviors, while children with ASD are more likely to have hoarding, ordering, and self-injurious behaviors (McDougle, Kresch, Goodman, & Naylor, 1995).

In both OCD and ASD, repeatedly performing behaviors or rituals may help reduce anxiety. For someone with OCD, the anxiety may be related to what will happen if he can’t engage in the behavior (for example, he may become ill or someone will be hurt). For someone with ASD, engaging in these same behaviors may be comforting, calming, or just interesting.

Children with ASD are not always able to accurately self-report whether or not feelings of distress accompany the obsessive-compulsive behaviors. This is a key component in the diagnosis of OCD. It’s often this distress that can help differentiate between a child engaged in self-stimulatory or stereotypic (repetitive) behaviors, and a child engaging in ritualized behaviors to relieve anxiety or distress from obsessive thoughts.

Psychotic Disorder
In the past, individuals diagnosed with a psychotic disorder. As more information and better assessment methods have become available, there have been far fewer misdiagnoses. Unfortunately, some children and adolescents still do receive an incorrect diagnosis of psychotic disorder when an ASD diagnosis would be more appropriate. When a psychotic disorder is suspected, it’s important to consult a professional experienced in working with psychotic disorders and ASD, and who also has expertise with differential diagnosis.

Here are some of the difficulties with making this differential diagnosis:

Children with ASD may engage in behaviors that appear strange or psychotic in nature. For example, a child may replay scenes and/or monologues from preferred television programs over and over. He may insist that he is the character in the program, or have difficulty communicating how he can tell the difference between fantasy and reality. He may get upset and engage in inappropriate behaviors such as yelling or aggression if you question him about his beliefs. This response is more likely tied to one of the primary characteristics of ASD— fixated interests and a desire for sameness. But the focus on fantasy characters and an insistence that these beliefs (which are not grounded in reality) are accurate often result in a diagnosis of a psychotic disorder by diagnosticians less familiar with ASD.

Children with ASD may also report hearing voices. Although this could be a psychotic symptom, this should not be assumed. A child with ASD may be referring to hearing his own thoughts, hearing things people have said to him in the past, or hearing the voice of someone who is in the next room.

Children with ASD have been known to talk to themselves or mumble under their breath. This behavior may reduce anxiety or may be a way to comfort themselves in unfamiliar surroundings or anxiety-producing situations.

One Comment

  1. Renee May 10, 2021 at 5:47 pm - Reply

    Thank you for touching on this subject. Exactly what I am struggling with for myself and my daughter asd2 adhd etc

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