Not usually. As has been mentioned, psychogenic stuttering exists, but the majority of the time it's bad luck, so to speak. Stuttering shows high heritability, and high (but interestingly, not 100%) concordance in twin pairs. That it to say, it's highly genetic. That said, trauma, even mild trauma, is thought to contribute often enough that during fluency evals, speech therapists will often ask if there's been any major events recently -- moving, deaths of loved ones, etc. It doesn't have to be abuse, though I'm sure that that can do it to. My professor likened it to the X-gene, from the X-Men. You always carry the gene for it, but you often need some sort of emotional or mental trauma to trigger the "powers," or in this case, stuttering. I'm not fond of the analogy because I think it reads too much like calling stuttering a super power, but the core of it is relatable enough, I think. In those that *don't* experience any notable trauma (among them, myself and my professor), I suspect that we simply have what Dr. Barry Guitar calls a "high genetic loading." That is to say, we simply have more genetic predisposition to stuttering. Just so you don't think I'm some random dude saying this, I just graduated with my MA-SLP, and I studied under one of the leading individuals in the fluency/stuttering world.