www.psychologytoday.com/us/blog/1-2-3-adhd/202002/the-relationship-between-autism-spectrum-disorder-and-adhd

For years, the DSM stated that the diagnoses of ASD and ADHD were mutually exclusive. In the latest version of DSM, however, co-diagnosis is allowed. As it turns out, on the basis of simple symptom categorization, there is a fair amount of overlap between these two behavioral conditions. Here are some statistics: There is a 5-10% incidence of ADHD overall in children, and a 2-5% incidence of ASD. Based on DSM-5 criteria, around 50% of children diagnosable with ASD could also be diagnosed with ADHD, and around 15% of children diagnosable with ADHD could be also be diagnosed with ASD.