How Common is the Co-Occurrence of Autism and ADD/ADHD?

Autism Spectrum Disorder (ASD) and Attention Deficit Disorders such as Attention Deficit Disorder (ADD) or Attention Deficit Hyperactivity Disorder (ADHD) are neurological conditions that affect how a person’s brain functions. Given the shared neurological underpinnings, it’s common for individuals to be diagnosed with both disorders. However, the precise prevalence remains difficult to quantify due to overlapping symptoms and challenges in accurate diagnosis.

James Rodis, an expert in the field, has noted a range of 50-80 percent overlap between ASD and ADHD. This figure has been widely accepted, though the exact number remains uncertain. The diagnostic overlap often presents difficulties in accurately distinguishing between behaviors associated with each condition.

According to Additude, approximately two-thirds of children with ADHD exhibit co-morbidities, with ASD being one of the most common. Other studies suggest that nearly half of individuals with ASD also have ADHD. It may seem that this overlap is certain, but it’s more accurately described as a distinct possibility given the complexity of overlapping symptoms.

Survey Evidence and Voluntary Internal Surveys

Survey data from adult autistic social media groups reveal that more than half of autistic individuals seem to also have ADD/ADHD. These informal and voluntary surveys, conducted within close-knit communities, provide insights but come with their own limitations. The challenge lies in measuring and defining these conditions accurately, especially in a community where individuals are self-reporting.

Experts emphasize that measures of ASD and ADHD in children are not as straightforward as many assume. Control groups are often small and inherently biased, and combining aspects of these disorders can create hybrid effects that are not always clearly separable.

Based on anecdotal and expert data, an estimated 80 percent chance exists that an autistic person will also have ADHD. This figure underscores the complex interplay between these conditions and highlights the need for comprehensive, reliable diagnostic tools.

Terminology and Diagnostic Challenges

In the United States, the terminology for these conditions has evolved. Asperger’s Syndrome, once a recognized diagnosis, is now subsumed under Autism Spectrum Disorder (ASD). Historically, individuals with Asperger’s were not diagnosed with ADD or ADHD because their symptoms were considered part of the overall ASD profile. However, in the current framework, ASD and ADD/ADHD are not separate diagnoses; they can co-exist.

Since ADHD now includes what used to be separate conditions (ADD is now ADHD-I for Inattentive type), and there are distinct types of ADHD (H for hyperactive type and C for combined type), individuals with ASD can receive separate ADHD diagnoses if their symptoms meet the diagnostic criteria.

Understanding the co-occurrence of ASD and ADD/ADHD is crucial for effective treatment and support. Accurate identification and differentiation of these overlapping conditions are essential for providing appropriate care and interventions.