In my case it tends to be when I’m anxious or unconfident my stutter would happen. So I would agree that treating anxiety or confidence would be good. But I do believe that for others it may not be due to anxiety/confidence but rather the way you speak. Such as mouth movements, breathing, stretching (before speaking) and so on. Tbh for me it’s a combination of both, using techniques and being confident helps. I feel that when being anxious it causes our body to tense up which disrupts our speaking causing a stutter. Breathing in and out, and stretching my body would help relax my tension which certainly helps my stutter.