Autism and ADHD are linked to neighborhood conditions

Young people with autism who come from disadvantaged neighborhoods tend to have more severe symptoms of attention-deficit hyperactivity disorder (ADHD) than their peers from more advantaged neighborhoods, according to one finding of a new study led by researchers at the MIND Institute at the University of California, Davis.

This is the first time researchers have investigated how neighborhood factors are associated with ADHD in children with and without autism. The study provides new insights into mental health conditions and may inform public policy changes to improve health equity.

It was published in the journal Progress of JCPP.

We found that several neighborhood factors were strongly associated with ADHD symptoms in children with autism.”

Katrina Kalb, lead author of the study and a postdoctoral researcher at the University of California, Davis

“In this study, this effect was only found in children with autism, not in typically developing children or children with other developmental disorders. This suggests that if children with autism live in low-resource areas, their ADHD symptoms tend to be more pronounced,” Kalb said.

Symptoms of ADHD include increased rates of inattention, hyperactivity, and impulsive behavior. It is associated with:

• Problems with school performance or relationships with friends
• Low self-esteem and increased risk of anxiety and depression
• Increased likelihood of substance use disorders and accidents
• Emotional dysregulation and behavioral problems

Research expands findings from long-term studies

The researchers used data from two studies, the decades-long Childhood Autism Risk from Genetics and Environment (CHARGE) study, led by Ilva Hertz-Picciotto of the MIND Institute, and the ReCHARGE follow-up project.

CHARGE and ReCHARGE will assess how genetic, environmental and other factors influence development from early childhood (ages 2-5) through adolescence (ages 8-20).

The researchers looked at 246 children with autism, 85 children with developmental delays (but not autism), and 193 neurotypical children. They then applied a “child opportunity index” that uses census data to track more than 30 neighborhood characteristics, including socio-economic, green space, single-parent households, and the concentration of early childhood education centers.

The index covers three domains: education, health and environment, and social and economic resources. Higher scores indicate better health outcomes for children. Of the three domains, scores in education and social and economic resources were most strongly associated with ADHD symptoms.

The analysis found that Child Opportunity Index scores at birth were a strong predictor of adolescent ADHD symptoms in children with autism but not in the other groups, a finding that Kalb noted was unexpected.

“These findings are very concerning,” Kalb said. “Individuals with both autism and ADHD are likely already facing additional behavioral, cognitive, emotional and social challenges. Coming from a low-income neighborhood puts them at an even greater disadvantage. This adds to the evidence that we need more resources for underserved communities, especially those with autism-like conditions.”

The need for larger and more diverse samples

Kalb noted that further research is needed to determine whether the results apply to larger groups.

“It will be important for future studies to be larger and more diverse, as this will help us understand whether neighborhood environment also influences ADHD symptoms in non-autistic youth and other groups who were underrepresented in our sample, such as black, Asian, and Native American,” Kalb added.

Schweitzer, a co-author of the study, noted that these findings also provide clues about how preventive strategies can be implemented to reduce the risk of worsening ADHD symptoms.

“ADHD is highly prevalent in the general population and is common among young people with autism. If we can find ways to increase resources in these areas, we have the potential to improve academic, social, mental and physical health outcomes and reduce long-term economic costs, especially for young people with autism,” Schweitzer explained.

Kalb and Schweitzer believe their findings should encourage policymakers to provide more resources to underserved communities, and they hope that including the Child Opportunity Index and other community indicators will add new insights to future research to inform policy.