The symptoms of autism spectrum disorder in very young children may be masked by symptoms of attention-deficit hyperactivity disorder (ADHD), according to a new study. The study found that it took an average of 3 years longer to correctly diagnose children who had been thought to have ADHD.
This effect could lead to a significant delay in diagnosing autism and getting the proper treatment. With autism, early therapy has been shown to be effective.
Although autism and ADHD share some symptoms, genetic factors, and brain pathways, they are very different neurologic conditions. Among the symptoms they have in common are hyperactivity, impulsiveness, and inattention.
Researchers from Harvard Medical School and Boston Children's Hospital examined data on nearly 1,500 children with autism that was collected from 2011 to 2012 by the National Survey of Children's Health. They asked parents if their children had been diagnosed with ADHD or autism. They also asked the parents at what ages their children received their diagnosis. About 43% percent of the children had been diagnosed with both ADHD and autism, the parents reported.
About 40% of those children diagnosed with both ADHD and autism had been diagnosed with ADHD first, the study found. Eighty-one percent of the children who were initially diagnosed with ADHD were diagnosed with autism after age 6. Those diagnosed first with ADHD were nearly 17 times as likely to be diagnosed with autism after age 6 than those who only received a diagnosis of autism.
The children also were 30 times more likely to receive an autism diagnosis after age 6 when compared with kids who were diagnosed with ADHD and autism at the same time, or diagnosed initially with autism and later with ADHD.
The children were also found to be 30 times more likely to receive an autism diagnosis after age 6 when compared with those who were diagnosed with ADHD and autism at the same time, or those diagnosed initially with autism and later with ADHD.
The study was published online in advance of the October issue of Pediatrics.