Autoimmune disease can attack the brain, cause psychiatric symptoms
I'm going to take a wild guess that 90+% of things we describe as 'autoimmune' are in fact initially caused by some bacteria/virus/pollution we haven't yet identified.I'd like to see research done on mice to reduce the number of viruses and bacteria they are exposed to - for example by sterilizing all air, water, and food for many generations.    Then see which ailments go away.