science

I was going to comment the same. I'd add that that it's also important to remember that (as opposed to physical diagnosis) mental health diagnoses are descriptive, rather than predictive.

You can think of a mental health diagnosis like a bucket, where we put different symptoms that often occur together (but rarely all the same time) and then label the bucket, as in "depression". Then we try to figure out why there seems to be this relationship of symptoms, where they are coming from, and how to make it better; with part of the object of study being intangible.

With physical medicine, you can follow a tangible path from the symptom to the cause. If you have symptoms of Covid, you can test for the specific virus. And then "predict" what's going to happen and what to do about it.