Some initial questions

>I understand there are different types of stuttering, and I am not sure about
>the exact terminologies, but one might, for instance, start stuttering after a
>head injury (adult onset?). Let's just talk about "mild" vs "severe"
>stuttering.

Answers:
1. Acquired stuttering (sudden onset in adulthood) is rare and typically due to some brain injury.
2. The usual "developmental stuttering" is a childhood disorder that usually manifests itself between 2 and 9 years of age.

>Do these (mild and severe stuttering) have essentially the same etiology, with >severity being caused by additional layers of learned "bad habits" ? Or is there >something fundamentally different?

Answers:
1.Basically we do not yet know the etiology of stuttering.
2.However mild and severe stuttering appear to differ considerably in how they can be treated and how they respond to treatment.

>As a mild stutterer I have had the tendency to assume that the techniques I
>have used successfully to control my stutter are equally applicable to severe
>stuttering. Is this a good assumption? Is there value in questioning it?

Answer:
Effectiveness of techniques depends more on actual speech behaviors than on stuttering severity