How does one define “severe”? Stuttering is more than the disruptions in speech. I have treated clients who have very few dysfluencies but it impacts their self esteem and overall function to the point they are mute. I consider that to be a severe stutter. On the other hand, I have dismissed clients who have a lot of disruptions in their speech, but are eager communicators, have a rich social life and do not consider it a disability anymore.