https://www.scientificamerican.com/article/why-do-so-many-mental-illnesses-overlap/
Put another way, scientists say there exists a propensity to develop any of a range of psychiatric problems. They call this predisposition the general psychopathology factor, or p factor. This shared tendency is not a minor contributor to the extent to which someone develops symptoms of mental illness. In fact, it explains about 40 percent of the risk.
