Dr Barry Duel and colleagues at the University of California, Irvine College of Medicine found children with ADHD were three times more likely to suffer from bedwetting and poor bowel control than children without this behavioural disorder. ADHD children often have this kind of developmental problems. They have difficulties to get a correct awareness of bladder control.
Imipramin, a tricyclic antidepressant commonly used for bedwetting problems, is also a useful therapy for ADHD. So maybe there is a biological connection between these problems.