On the surface, symptoms of autism spectrum disorder might be masked by symptoms of attention-deficit/hyperactivity disorder. Researcher Vasiliki Kentrou explains how this masking could lead to a delay of an autism diagnosis, or even a misdiagnosis of ADHD: “Autistic children might be overactive or disruptive when they're playing with other children, which could be noticed by teachers and parents. However, they might only focus on the behaviours they can observe, instead of looking into whether autism is the child's underlying disorder.”
The researchers wanted to study if people who already had an ADHD-diagnosis had a different age at the time of getting an autism diagnosis, in comparison to people who only had an autism diagnosis. The study used data of more than a thousand autistic children, which had already been collected by past questionnaires from the Dutch Autism Register (NAR). Children and adolescents initially diagnosed with ADHD received an autism diagnosis an average of 1.8 years later than children with only an autism spectrum disorder.
The researchers also looked if the child's gender also influenced this delay in diagnosis. Boys with a previous ADHD-diagnosis got an autism diagnosis an average of 1.5 years later. Girls with an ADHD-diagnosis got an autism diagnosis an average of 2.6 years later. “A lot of diagnostic instruments were mostly developed for boys,” Kentrou explains. “But girls and boys present autism in a slightly different way. Boys might be alone in a corner or not interact much which their peers. But girls may try to initiate contact with their peers. Teachers, having been taught about autism via research done mostly on boys, may see this as a normal interaction, even if the girl fails to connect with her peers.“
Kentrou argues that screening procedures should involve multiple people, in order to accurately assess for potential hallmarks of autism in children and adolescents who are diagnosed with ADHD: “It is important to not only rely on one doctor, but get the assessment of other doctors and people who are involved with the child as well. Furthermore, it is important to rely on the proven standard tools to diagnose autism, as well as to keep developing those tools. Clinicians should stay informed about these latest developments, for example new findings in how autism presents in both children and adults.“
