This theory of humors formed part of the theoretical foundation of medicine in many cultures for centuries. It's no longer considered as mainstream medical theory, which does not mean it's not valid, it just means it's ignored. It's never been disproved...
Mainstream medicine is being controlled by Big Pharma these days, so if the "answer" to the problem doesn't involve expensive profitable drugs, the medical industry isn't interested. In the U.S., all a drug company has to do to get FDA approval for some drug is to present 3 "positive studies". It doesn't matter if there are 10 studies that show it's useless or even harmful.
Mainstream medical doctors used to open up the doors of the insane asylums and allow the more sociopathic members of society to come in and verbally and physically abuse the inmates for "fun".
Later, patients with mental problems were the victims of experiments using electrocution and hallucinogenic drugs.
The history of mainstream medicine in any era has hardly been a picture of ethics and compassion and theories tend to be replaced on a regular basis (unless they're just entirely too profitable, like the trillions of $$ spent on chemotherapy, which is repeatedly shown to be useless).