I don't know of any literature that directly links headaches to ADHD. But ADHD can increase stress, and stress can cause headaches. Keep track of when your headaches occur, and make sure that your symptoms are covered by medication at times when stress is likely. Headaches can also be a side effect of stimulants. Ask your doctor about stopping your medication for a period of time. If the headaches go away, consider switching to a non-stimulant.