Hi,
Yes, adults and children with ADHD can have stuttering problems. In fact, it's thought that up to 26% of children with ADHD also have a stuttering problem.
It's not known why this may be; perhaps it's a neurological issue. But others feel that it may have to do with the hyperactive/impulsive nature of the beast. Those with ADHD often have rushing thoughts that they try to get out, either out of impulsivity or because of a fear that they'll forget what they're trying to say.
If your husband is bothered by this, he should consult with a speech and language therapist.
Hope this helps!
Terry