Acute psychosis could be an immune response to the presence of certain microbes,
or their detritus, in the central nervous system. In fact, this is known to be the case for rabies, which causes larger mammals infected by the virus responsible for the symptoms to behave in ways once attributed to insanity and, before that, to demonic possession.
The problem is that no one seems to want to do research on that possibility. And it is too bad that if the symptoms of acute psychosis have an epidemiological cause, the natural immune response of which those symptoms are a byproduct is so often interrupted by the use of chemical straitjackets before it can succeed in its purpose and restore the patient to health. Because of such "therapy," countless people may be condemned to lifelong "possession" -- i.e., infection -- by the microbial agents responsible for their condition.