What research are you referring to? I have never come across such research in any of the psychology journals I have read.

In my experience, T's without medical training or doctorates do not typically use "patient."

I use client, and I would correct a T who tried to use "patient." I do not have a mental health diagnosis and I do not seek medical treatment for any mental health concerns. I see an LCSW because I find it beneficial to talk things out with her. I am her client; I am not her patient. She has no medical training, so I would find it very odd if she suddenly started calling me a "patient."