Dr. Sandra Kooij is a good person to look up if you are interested in adult ADHD and sleep. She has a book about it. From what I remember, there are a few things that are known:

1. a large majority of ADHD sufferers are phase-delayed and struggle with insomnia

2. you can induce ADHD-like symptoms in normal people by restricting sleep

3. Some of the interventions that improve sleep timing and quality affect ADHD (but it isn't a total cure)