There are two ‘new’ theories that I think are conjoined. The first which has came from America and is being championed by good Allopathic American MD’s which is the idea commonly called leaky gut which may be responsible for many auto immune diseases. And in conjunction to resulting breakdown of the brain blood barrier may well be the cause of many of todays common diseases from Alzheimer’s to psychosis and schizophrenia. Given that 35% of the population do not have the main polymorphic variant of the HLA-DQ gene and protein and high instances of poor diet in populations it is very likely that there are many cases of undetected leaky gut. The second theory which is more proven and has actually been around since about 2003 is that of encephalitis psychosis which is where sites on the brains neurons are attacked by the immune system.
The American leaky gut theory suggests that breakdown of the gut-blood-barrier due to the gliadin gluten from wheat grains results in production of antibodies to gluten in the blood steam. These gluten antibodies in turn attack the blood-brain-barrier which is made of transglutimase 2. Then which in turn breaks down and is released into the blood steam and the body then produces antibodies to the transglutimase which then further breaks down the blood-brain-barrier.
My two resulting theories are that the first causes the second. Once the blood-brain-barrier is broken antibodies then attack glutamates in the brain and can also cause further damage leading to degenerative brain diseases.
Healing the whole process and reducing the antibody levels in the blood starts with healing the gut. First stop all grains other than grains like buckwheat and oats. Regenerate the gut flora with good bacteria like sauerkraut (ideally organic non pasteurized sauerkraut), tempeh, and capsule form probiotics.
Further more complex immune system therapies are available from specialized clinics but I really suggest that the gut-blood-barrier and gut health are the key to stopping the root causal mechanism.
This is only a summary. I will further expand this and add references later.