Is adhd related to autism?

No: They are both neurobiologic disorders, but of different genetics, inheritance, causation (probably) & severity. Different brain areas are involved in these conditions. But autistic kids can have add, which makes managing their ad more difficult.

Only by the brain: Adhd is a problem with the brain being able to pay attention. Autism is a problem with the brain being able to connect to other people, to relate, and to interact. They are not the same thing. But all functions of the brain are related since the brain is one organ.

40-70% of folks with: Autistic Spectrum Disorder also have ADHD. Signs of adhd = inattention, hyperactivity & impulsivity. Signs of ASD= impairments in social communication & reciprocal social interaction + stereotypies or narrow, restricted areas of interest, so they are different neurodevelopmental disorders that can co-exist. ASD also can co-exist with Intellectual Disability, Anxiety Disorders & Depression.