There are studies that show a link between inflammation and psychotic disorders, and inflammation and neural sensitization (multiple chemical sensitivity, or MCS). Many MCS patients also reported some associated psychological symptoms. The chronic, systemic inflammation is found in susceptible people due to repeated activation of immune cells. A good place to learn more about this is on http://www.iaqradio.com
and click on "Go to Show". From there click on episodes 79 and 80 with Dr. Ritchie Shoemaker.