I feel like there have been studies with hallucinogens and depression but not stuttering. Just seems like whether someone stutters or not is easier to measure than depression. Once I used DXM and about halfway through I came to the realization that I didn’t stutter. I just convinced myself it was a habit I broke myself of. The next day I went to work and did not stutter at all. The day after I started stuttering again, but it slowly built up to my normal level. The other experience was actually THC, but it was super strong and I am sensitive to the effects of THC so I had that trippy feeling. I went to bed that night, woke up went to work and did not stutter for two days. Both times when the stutter returned I felt like crying. This has been about 10 years ago.