Does a "P-factor" Underlie Core Attributes of Mental Health Maladies?

I want to point to an open source "Core Concepts" article in PNAS by David Adam that presents "the views of some psychiatrists who argue that the same bit of biology—genetics gone awry or some misplaced brain circuitry—could underlie the vast majority of humanity’s mental health problems. Studies have shown, for example, that many of the same genes seem to drive increased risk for autism, attention-deficit hyperactivity disorder (ADHD), bipolar disorder, major depression, and schizophrenia. They call this as-yet-unidentified common cause the “psychopathology factor,” or “p-factor” for short."