How much research has gone into the psychological aspect of stuttering?

How much research has gone into the psychological aspect of stuttering? Before I start, some background. I'm 18, I've been stuttering since 6th grade. Growing up, I talked really fast (I feel this may have been the start of it all), but I was completely fine before then, my speech impediment was purely struggling with pronouncing my r's. I was bullied (for reasons to this day I cannot pin down) to the point where I was scared to speak. From there, my stammer became a stutter It was slow at work, and I got into a discussion with my McDonalds managers about my stutter, and it really got me thinking. Could a stutter be more psychological than physical? Just think about it. I've noticed a lot of things about my stutter (I'm 18, been stuttering for 6ish years) and I'm sure most of these apply to others as well Have you ever noticed that you don't stutter when in a room by yourself? Not even in a room by yourself, next time you're out in public go ahead and whisper to yourself, you'll find that you don't stutter. I think this ties into the anxiety part of it all. I'm sure many of us fear conversation, whether it's ordering food, being forced into a conversation, and even standard dialogue. I myself am an introvert and extremely shy (a shame really, my sense of humor is second to none), but something I've noticed is that my stutter is considerably less noticeable when conversing with friends and family. Even when talking to the co-worker I have a crush on, if I'm comfortable talking to the person, I don't stutter Throughout my days of middle school and high school, I would struggle with answering and talking in general in high school. But if my teacher ever asked me to read something from a textbook, my stutter would be minimal to none, and people noticed. I think this ties into it being a pre-prepared sentence. When I stutter, I need to pause and think about how to phrase it, but books and other things do that for me. It's like when I'm singing a song, I don't stutter. I could be in the middle of a football field, stuttering during a conversation, but I'd be able to sing without an issue I still can't wrap my head around all this, and it honestly frustrates me. I went to the best speech therapist in the state of NH, and she struggled with my sessions because I would barely stutter when talking to her. Here I am, sitting in her office working on stuttering less, and she tells me I stuttered 2 or 3 times during the entire hour long session. But I walk out that door and struggle to say "bye, have a nice day" to the receptionist I hope I grow out of this. I wasn't born with it, so it should surely go away, right? I didn't even know this was possible until a few of my co-workers (would work with them every Sunday) told me that they grew out of theirs. They told me to "relax". Being anxious, shy, and an introvert, I struggle with it. But, whenever I think about it, I'm able to speak more fluently. But, the second I think "wow, I'm talking really well" BAM, I struggle with the next word While it may be frustrating, damn can this stutter be fascinating