The immune system has many ways in which it causes problems for us, rather than the bacteria, viruses and other pathogens it should be focusing on.
We call this auto-immune disease. Depending on the area affected, auto-immune disorders get different names. For example, rheumatoid disease affecting joints or psoriasis affecting skin. But it’s all the same issue.
When it comes to the mind and psychological or psychiatric disorders, the traditional assumption has been that the problem is localised in the brain itself, with or without stress or adverse life experiences as a cause or trigger.
The idea that the immune system could attack or interfere with the brain enough to cause depression or psychosis has only been recognized in the last five years or so.
For example, some new research in January 2018.
And this new centre at a Sussex NHS Trust.
Or listen to this excellent podcast from the BBC for some more information.