ADHD News & Research

Early ADHD Diagnosis May Affect Autism Diagnosis

Children with comorbid ADHD and autism whose ADHD was diagnosed first may experience a delay in receiving an autism diagnosis.

September 18, 2016

Being diagnosed with ADHD may result in as much as a three-year delay in the diagnosis of autism when the conditions coexist or symptoms overlap, a new study finds. This raises important questions about diagnosis standards and the best age for beginning treatment.

The study, published in Pediatrics, found that children with both ADHD and Autism Spectrum Disorder (ASD) — whose ADHD was diagnosed first — were 16.7 times more likely to have received their ASD diagnosis after the age of six. The American Academy of Pediatrics (AAP) recommends doctors watch for an ASD diagnosis between the ages of 18 and 24 months, using a multi-step process that combines parental surveys, family history, developmental milestones, and careful observation of the child during visits. The study also found that about 40 percent of all children weren’t diagnosed until age six or later — but the delay was most troubling when an early ADHD diagnosis existed.

Researchers looked at data from the 2011 and 2012 National Surveys of Children’s Health, examining nearly 1500 children between the ages of two and 17. The results remained consistent even when researchers controlled for potentially confounding factors like race, income level, or severity of ASD. The investigators also directly compared children who had been diagnosed with ADHD first with children who had received their ADHD and ASD diagnoses at the same time. The results held true, showing a 3.2-year delay in ASD diagnoses when ADHD was diagnosed first.

The results should encourage the medical community to reexamine its diagnosis guidelines for ADHD and ASD, the researchers write, as well as take potentially overlapping symptoms into account. Children diagnosed with ADHD before ASD may “exhibit unique dimensional traits that could bias clinicians toward an ADHD diagnosis. To avoid potential delays in ASD diagnosis, clinicians should consider ASD in young children presenting with ADHD symptoms,” they add.

Early diagnosis for autism is especially important, says lead author Amir Miodovnik, M.D., as it gives children and parents a jump-start on treatment.

“It’s been shown the earlier that you implement these therapies for autism, the better children do in terms of outcomes,” Miodovnik said. “Three years is a significant amount of time for the kids to not be receiving therapy.”