Health is good, of course. ;) I think you've sort of reversed the quality of life angle. When we get better at managing or dealing with our stutter, our QoL improves. Having a better mood in general probably makes stuttering incidents easier to cope with, but it doesn't necessarily make you better at stuttering. At any rate, health and stuttering aren't mechanistically connected. Otherwise, every stutterer who was in good health wouldn't really be stuttering, and every stutterer with poor health would have immense difficulties. This is not our discovery, though.