Co-occurring Conditions: Autism and ADHD, Anxiety, and More

Autism does not exist in isolation. The majority of autistic people have at least one co-occurring condition — another neurological, psychiatric, or physical condition that intersects with and complicates their autistic experience.

Understanding what those co-occurring conditions are, and how they interact with autism, is essential for families trying to understand their child and get appropriate support.

ADHD

ADHD is the most common co-occurring condition in autism. Studies suggest that between 50 and 70 percent of autistic people also meet diagnostic criteria for ADHD. The two conditions share several features — difficulties with sustained attention, impulsivity, executive function challenges — but they are neurologically distinct.

For a long time, the DSM did not allow dual diagnosis of autism and ADHD. This changed with the DSM-5 in 2013. Before that, many children with both conditions were diagnosed with one and missed the other — meaning their treatment and support addressed only part of what they were dealing with.

The interaction of autism and ADHD is complex. ADHD can amplify sensory sensitivity. Autism can affect how ADHD presents. Both conditions affect executive function. Getting an accurate picture of what is happening requires evaluation that looks at both.

Anxiety

Anxiety is extremely common in autistic people — estimates range from 40 to 80 percent, depending on the study and the diagnostic criteria. And it makes sense: navigating a world designed for neurotypical processing, while masking, managing sensory overwhelm, and dealing with unpredictability, is anxiety-producing.

But anxiety in autistic people can look different than anxiety in neurotypical people, and this can lead to misdiagnosis. An autistic person whose anxiety manifests as insistence on routine and resistance to change may be diagnosed as having a behavior problem rather than an anxiety disorder.

Treating anxiety in autistic people requires approaches that account for the autistic nervous system. Standard cognitive behavioral therapy may need modification. Sensory accommodations that reduce overall load may reduce anxiety significantly. Predictability and routine — which reduce the cognitive cost of navigating the environment — can have a significant anxiolytic effect.

Sensory Processing Disorder

Sensory processing differences are now considered part of the diagnostic criteria for autism, but some children have sensory processing difficulties that do not meet the full criteria for autism diagnosis. Occupational therapy with a sensory integration focus can be helpful for both.

Gastrointestinal issues

The gut-brain connection is well established, and autistic people have higher rates of gastrointestinal issues than the general population — constipation, food sensitivities, and other digestive difficulties. These can contribute to behavioral and emotional regulation difficulties in ways that are sometimes misattributed to the autism itself.

What this means for families

If your child has been diagnosed with autism, it is worth asking the evaluating clinician whether there may be co-occurring conditions that should also be evaluated. An incomplete picture leads to incomplete support. A full picture leads to better interventions, better accommodations, and a better understanding of what your child is actually dealing with every day.