You'll have to do independent investigation into it. Do you notice that you stutter more or less (to a significant enough degree) with friends. I know certain of my friends I stutter around significantly more. Took me a while to figure it out. Some factors I found are 1) how authentic are you "allowed" to be around your friends, 2) How patient are your friends. Do they accept your stutter? Do they interject while you're speaking? Even if they don't interject, you might feel they are about to on a subconscious level, causing you to tense up