Any sources for this Autism plus ADHD thing? Google seems a bit vague. All I can find is it's about 30% prevalence of ADHD with Autism, and it could be the root cause of most of the Anxiety/Depression cycles which are otherwise hard to treat in Autistic folk.
Which is, you know, seems familiar. Also, the ADHD part, and thus the Anxiety/Depression cycle, can basically be medicated away. I guess there's better places to ask, but yeah, on my mind lately.
There’s an overlap between autism spectrum and ADHD in the experience of sensory overload, so some association should be expected, though that doesn’t necessarily mean they share any direct cause. (E.g., if both conditions put stress on the same systems, then having one condition makes it harder to compensate for the other, and each would be more likely to be diagnosed when occurring together.) Overload is also one obvious cause of anxiety, so that’s another expected association.
Some association with introversion might also be expected (because introversion is largely an expression of high stimulus sensitivity), which fits the popular stereotype of autism; but I’m not aware if any association has actually been shown between introversion and ADHD.
[Standard caveat applies: individuals may vary.]