Children with autism spectrum disorder (ASD) often have symptoms that look like those of attention-deficit/hyperactivity disorder (ADHD). Could this similarity delay an ASD diagnosis in some children? A national study last month in Pediatrics, involving nearly 1,500 children with an ASD diagnosis, found the answer is yes.
Of the 1,500 children, about 20 percent were initially diagnosed with ADHD. On average, they received their ASD diagnosis about three years later than those who were first diagnosed with ASD or with both ASD and ADHD simultaneously. This made them 30 times more likely to be over the age of 6 when diagnosed with ASD, missing a vital intervention window.
Notes talked to the paper’s first author, Amir Miodovnik, MD, MPH, of Boston Children’s Hospital’s Division of Developmental Medicine. (Miodovnik currently practices at The Maimonides Infants & Children’s Hospital in Brooklyn, NY.)
Q: How can autism masquerade as ADHD?
Children with autism often manifest behaviors such as inattention, hyperactivity and impulsivity that are commonly associated with ADHD. These behaviors may overshadow or mask the social communication deficits, restricted interests and repetitive behaviors that are the core symptoms of ASD.
Seeing that these behaviors can also contribute to functional impairment at home and in school, a provider may diagnose ADHD, one of the most common and treatable neurobehavioral disorders of childhood.
The core symptoms of autism may not always be present at each routine visit, and when they do appear, they can be relatively subtle or nonspecific in the context of a clinic setting. The co-occurrence of ADHD symptoms can make differentiating ASD from ADHD more difficult, especially for less severe cases of ASD in young children.
Q: Autism can be reliably diagnosed in children as young as 24 months. What are the implications for the patient when the diagnosis is delayed?
Behavioral therapies appear to be most effective if started by preschool age or younger. Autism that goes unrecognized and untreated until the child is older may negatively impact that child’s long-term prognosis.
Children with autism often manifest behaviors…that are commonly associated with ADHD
A 2001 review by the Committee on Educational Interventions for Children with Autism (formed by the National Research Council) concluded that early intensive behavioral intervention for children with autism (also known as applied behavior analysis, or ABA), resulted in substantial improvements in IQ, language, adaptive behaviors and educational placement when initiated at preschool age and sustained for at least 2 to 3 years. Subsequent reviews have also found that ABA starting before 4 years, conducted for at least 20 to 30 hours per week, takes advantage of young children’s neural plasticity and helps prevent them from falling further behind their peers.
While many older children also benefit from ABA and can increase their level of overall functioning, losses in skills are more difficult to recoup the longer you wait.
Q: Is there anything physicians should consider doing differently based on these results?
AAP guidelines recommend universal screening for ASD at 18 and 24 months of age. In addition to routine autism screening, providers should elicit parental concerns about social development and speech delay and, whenever possible, directly observe the child’s language and play skills.
Parents can be asked to fill out the first stage of the Modified Checklist for Autism in Toddlers Revised (M-CHAT-R) prior to the appointment. This 20-item questionnaire is freely available online at m-chat.org and takes about 10 minutes to complete. If the child screens positive, providers can schedule a follow up visit to administer the second stage of the M-CHAT-R (called the Follow-Up), which is composed of interview questions. If the child again screens positive, he or she should be referred promptly for an early intervention assessment.
Very young children in whom ADHD is being considered as a potential diagnosis should be referred for a comprehensive evaluation by a specialist, or at the very least, they should have a free developmental assessment through the state’s local early intervention program.