With certain children, it can be hard to tell the difference between an Autism Spectrum Disorder (ASD), Attention Deficit Hyperactivity Disorder (ADHD), and Oppositional Defiant Disorder (ODD). You may see a child with just one of these, but it may not be clear which diagnosis would provide the most thorough and helpful way of describing the child’s differences (which is the point of coming up with a diagnosis, since for the most part diagnoses are just shorthand descriptions of behavior). Alternatively, you may frequently see a child with more than one of these problems.
Autism Spectrum Disorder
A core difference seen in children with ASDs is a difference in the ability to relate socially to others. They may show difficulty putting out effort in areas that are not of special interest to them (mimicking ADHD) or they may be defiant with requests for compliance (mimicking ODD) especially if the task interferes with one of their preferred activities, but along with that they have significant differences in their social relationships which may range from just awkward or odd to a complete lack of interest in other children. They may not show a broad range of facial expressions, use gestures or be able to demonstrate perspective taking skills or empathy.
Attention Deficit/Hyperactivity Disorder
The core issue in children with ADHD is difficulty with inattention and/or hyperactivity and impulsivity. Children with ADHD are frequently immature in their social skills, and may appear a couple of years behind in their social development. However, a child with ADHD and not an ASD would still be able to engage in perspective taking and have empathy. According to the diagnostic criteria, ADHD is not supposed to be diagnosed in someone on the autism spectrum, but in actual practice this is not followed, and these disorders are frequently diagnosed together. This in part may be because there are medications available to reduce symptoms of inattention, hyperactivity and impulsivity, but there are none that address the core ASD symptoms.
Oppositional Defiant Disorder
The core issue in children with ODD is a pattern of negative, hostile and defiant behavior. Many of these specific symptoms are seen in a verbal ASD child, such as blaming others, arguing or defying requests for compliance. One way to look at the difference is that a high functioning ASD child may comply when the request makes logical sense to them rather than being always defiant no matter what is asked. An ODD child often argues with adults, whereas some ASD children will get along better with adults than other children, since he or she may act more like a short adult (the little professor type) than a child.
It isn’t unusual for a young child to initially be diagnosed with ADHD and ODD, and then later the diagnosis is better clarified and changed to an ASD. The ADHD and ODD may then get dropped, or continued if they are still areas of clinical attention.
For example, I have had a child come in to see me who was previously diagnosed with Asperger’s Syndrome, but I observed the child showed a full range of affect, was very empathic and intuitive, and had many friends although those friends tended to be a year or two younger. However, the child put out little effort in school, and had to be reminded many times to complete chores and homework. This child was better diagnosed as having ADHD, inattentive type than with Asperger’s Syndrome.