The rate of comorbidity of ASD and ADHD could further differ across estimates when the population of focus is children with ASD. In a sample of children identified as having ASD per parent report, found that the 20% of children diagnosed with ADHD before ASD received their ASD diagnosis approximately three years later than the group including children that were diagnosed with ADHD and ASD simultaneously, as well as later than the group including children with ADHD diagnosed after ASD.
The children with ADHD diagnosed first were 30 times more likely to receive their autism diagnosis after the age of six. This suggests that when samples comprised mostly of young children, especially those under age six are studied, the resulting prevalence estimates for ASD could be understated. This conclusion is further supported by the finding that many children do not receive an ASD diagnosis until they approach school age.
Experts noted that it can be difficult to isolate a diagnosis of ADHD or ASD since the symptoms often overlap. What’s more, the symptoms of ADHD are often the same behaviors exhibited in typical childhood development—except that they persist and worsen over time.
As far as what’s different one study says “ADHD is defined by impaired functioning in the areas of attention, hyperactivity, and impulsivity, whereas ASD is characterized by core social dysfunction and restrictive-repetitive behaviors.” These ASD trains iinclude behaviors such as:
Available research on the comorbidity of ASD and ADHD is still scarce because prior diagnostic standards made the diagnosis of one an exclusion for the other. However, when the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was published in 2013, it included criteria that allowed clinicians to diagnose an individual with both disorders at the same time.
With the ability to better understand the impact of ASD and ADHD as comorbid conditions, more accurate diagnoses and more effective treatment options may be available. For students with these conditions, such insight gives educational professionals such as school counselors a better understanding of what strategies they can use to help these children and their parents to succeed.