Stuttering stems from anxiety?

Stuttering stems from anxiety? Ever since I was in middle school, I’ve had a stuttering problem. What I’ve noticed though is that I don’t stutter when I’m alone and I don’t stutter when I’m with family and close friends, people I see every day. I only stutter when I interact with strangers or people I haven’t seen in a long time. What does this mean? How can a stutter only activate around certain people? Is my stutter purely anxiety based? I wish I could just get rid of this thing.