According to new research carried out at the Kennedy Krieger Institute, nearly a third of children with autism spectrum disorders (ASDs) between the ages of four to eight also showed clinically significant symptoms of attention deficit hyperactivity disorder (ADHD).

The study, which was published in Autism: The International Journal and Practice, identified a significant co-occurrence of ADHD and ASD.

The researchers identified that children with ASD who showed signs of ADHD were much more likely to have impaired cognitive, social and adaptive functioning, compared to children with just an ASD.

Social problems in children with autism and ADHD were had been analyzed in a previous study, which revealed that children with both autism and attention deficit or attention deficit hyperactivity disorders are four times more likely to bully than children in the general population.

Most previous studies that have identified a link between ASD and ADHD have been based on patients seeking treatment from clinics (which makes them biased towards patients having more impairments). However, this current study provides a more accurate analysis (with reduced bias) of the link, as it only included infants or toddlers – before most cases of ADHD are diagnosed.

Dr. Rebecca Landa, the senior author of the study and director of the Center for Autism and Related Disorders at Kennedy Kriegar, said:

“We are increasingly seeing that these two disorders co-occur and a greater understanding of how they relate to each other could ultimately improve outcomes and quality of life for this subset of children.The recent change to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to remove the prohibition of a dual diagnosis of autism and ADHD is an important step forward.”

A total of 162 children participated in the longitudinal child development study. The investigators split the children into two groups:

  • with ASD group
  • without ASD group

The groups were further according to ADHD classification – based on a standard ADHD symptoms assessment Hyperactivity and Attention Problems subscales of the Behavioral Assessment System for Children-Second Edition.

63 of the children were diagnosed with ASD, of whom 18 (29 percent) showed clinically significant symptoms of ADHD.

The authors stress that this study represents a “younger and narrower sample” compared to previous studies.

Landa added: “We focused on young school-aged children because the earlier we can identify this subset of children, the earlier we can design specialized interventions. Tailored interventions may improve their outcomes, which tend to be significantly worse than those of peers with autism only.”

Children diagnosed with ASD who also had ADHD symptoms were much more likely to have significant cognitive delays, and more severe autism mannerisms such as repetitive behaviors, compared to those with only ASD (61 versus 25 percent).

The authors suggest that this information could help improve treatment options for children with ADHD who have also been diagnosed with an ASD. According to a previous report published in Archives of General Psychiatry, Methylphenidate, an ADHD drug, may be effective in treating hyperactivity symptoms in children with autism and related pervasive developmental disorders.

Written by Joseph Nordqvist