I had anxiety attacks and back pain for years. Maybe it’s just a weird and strong placebo effect, but after starting to take vitamin D these things were simply gone.
I found the same - I was starting to get anxiety first thing in the morning - started taking Vitamin D and it simply stopped. At the time I had no idea that Vitamin D could have that effect.
My allergies started to dramatically improve after taking 8-10k IU vitamin D daily. This isnt medical evidence and may be pure luck but I am just adding to the anecdotes.