To me these DSM concepts are not about diagnosis or etiology. They are about grouping of behavior and symptoms for the purpose of facilitating the machinery of industrial and mainstream healthcare.

Most MH professionals probably do not know enough to sift through all of the possible causes, and perform differential diagnosis. Most therapists I have been to, for example, knew nothing about bodily disease as cause of mental disturbance. They have a narrow worldview. Psychiatrists too from what i've read. Lots of vague talk about environment vs genetics.

There is apparently strong correlation between exposure to cats in childhood, and later development of schizophrenia and BPD, among other things. This is because cats transmit a parasite called Toxoplasma to humans. This microbe targets brain cells in humans. I'm guessing this not covered in the DSM nor known by many MH practitioners. Just one example.