Some researchers now believe that schizophrenia is caused by an interaction of an infectious agent, particularly a virus, with a genetic predisposition to the illness. There are a number of features of known viruses that might make this possible:
- Viruses can attack certain brain regions and leave others intact.
- Viruses can alter certain processes within a brain cell without killing the cell.
- Viruses can infect someone and then lay dormant for many years before causing illness.
- Viruses can cause the minor physical abnormalities, birth complications, and altered fingerprint patters sometimes found in people with schizophrenia.
- Viruses can affect neurotransmitters.
- Some antipsychotic agents are also antiviral agents.
People who have recently developed schizophrenia very often have antibodies to two herpes viruses in their blood, HSV (herpes simplex virus) and CMV (cytomegalovirus). Studies have shown that when these herpes viruses infect someone with a particular set of genes, that person is much more likely to develop schizophrenia.
People with schizophrenia also are more likely to show antibodies to toxoplasmosis gondii, a parasite carried by cats that can also infect humans. Being raised around cats slightly raises a person’s likelihood of developing schizophrenia, and the illness is more common in countries and states where many people have cats as pets.
Infectious disease theories of schizophrenia are very exciting and promising. It is too early to know if researching these theories will reveal the cause of schizophrenia.