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ADHD symptoms can delay autism diagnosis for years

Researchers urge doctors to fully evaluate young children with attention deficit/hyperactivity disorder for co-occurring autism
September 14, 2015

A new study finds that the symptoms of attention deficit hyperactivity disorder (ADHD) can significantly delay the recognition of autism in children. Because early intervention is so important with autism, the researchers urge doctors and others who screen for such disorders to carefully evaluate for autism in children with ADHD.

Their findings appear online today in the journal Pediatrics.

Previous research suggests that more than half of children with autism also have ADHD or some of its symptoms. Not only do the two disorders frequently occur together, they share many red flag behaviors – including inattention and impulsivity.

In the study, researchers at Boston Children’s Hospital reviewed information from the National Survey of Children's Health on nearly 1,500 children, ages 2 to 17 years with autism spectrum disorder. Their important findings included:

* Approximately 1 in 5 children diagnosed with autism had an earlier diagnosis of ADHD.

* On average, the children initially diagnosed with ADHD received their autism diagnosis 3 years later than the children who had autism but no prior ADHD diagnosis.

* Overall, the children with ADHD were nearly 30 times more likely to receive their autism diagnosis after age six.

* The delay in diagnosis proved true regardless of the child’s age or severity of autism symptoms.

 The authors suggest that part of the issue is that symptoms of inattention and hyperactivity tend to become obvious earlier than autism’s social communication challenges and repetitive behaviors. As a result, ADHD symptoms may overshadow the core symptoms of autism, making the latter particularly challenging to recognize in these children.

The authors urge doctors to rigorously follow the American Academy of Pediatrics guidelines for universal screening for autism spectrum disorder at 18 and 24 months of age. They should also consider referral to a specialist in autism when autism and ADHD symptoms seem to co-occur.

“This study shows how difficult it can be to diagnose autism and differentiate it from a complicated case of ADHD,” comments developmental pediatrician Paul Wang, Autism Speaks head of medical research. “Sometimes it takes evaluation by a team of experts to tease symptoms apart.”

The bottom line, Dr. Wang says: “If parents or others have any concern about autism, it's critical to get a truly expert evaluation. The right diagnosis is absolutely needed, so that the right interventions can be put in place.”

Editor’s note: With 14 sites across the US and Canada, Autism Speaks Autism Treatment Network provides coordinated, multidisciplinary care to assist children with autism and their families - including those with complex behavioral and medical needs. 

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