Schizophrenia's a complex one. It seems to be associated with human endogenous retrovirus-W (HERV-W):
>Several other studies have since found similar active elements of HERV-W in the blood or brain fluids of people with schizophrenia. One, published by Perron in 2008, found HERV-W in the blood of 49 percent of people with schizophrenia, compared with just 4 percent of healthy people. “The more HERV-W they had,” Perron says, “the more inflammation they had.”
The odd thing is HERV-W is a viral sequence which entered the human genome many millions of years ago. It is normally suppressed but can cause problems sometimes triggered by other infections.
>Several other studies have since found similar active elements of HERV-W in the blood or brain fluids of people with schizophrenia. One, published by Perron in 2008, found HERV-W in the blood of 49 percent of people with schizophrenia, compared with just 4 percent of healthy people. “The more HERV-W they had,” Perron says, “the more inflammation they had.”
The odd thing is HERV-W is a viral sequence which entered the human genome many millions of years ago. It is normally suppressed but can cause problems sometimes triggered by other infections.
http://discovermagazine.com/2010/jun/03-the-insanity-virus