> I'm not disagreeing, but is this something that everyone reasonable would agree on without any sort of support?

Somehow, the field of psychiatry doesn't seem to actually act on it.

Or they do, since they prescribe drugs which are designed to cross the blood-brain barrier, but even when they decide to prescribe drugs, they don't actually do any kind of blood tests to determine which drugs are likely to be effective.

They prescribe drugs based on simply you talking about your own symptoms, or observing your symptoms, and then just trying things until they find something that works or that you report works. They don't even seem to use any kind of formal testing of cognitive functionality to determine what effects the drugs are having; they just rely on purely subjective chats with the patient.