In addition to the genes implicated in schizophrenia, a number of environmental risk factors have been implicated in the disease.These include effects during fetal development (famine and maternal infection during pregnancy) as well as during childhood and adulthood. These factors are compiled in this table. Starvation and viral infection activate the eif2alpha kinases gcn2 and pkr, leading to inhibition of the translation initiation factor eif2b, and the arrest of protein synthesis. EIF2B is paricularly important in the control of oligodendrocyte function, and activation of these pathways by some of the risk factors might be related to the oligodendrocyte cell death observed in schizophrenia. Further details

Risk factor	Reference (and related)
Maternal Famine	St Clair et al, 2005
Prenatal Rubella infection (first trimester)	Brown et al, 2000
Maternal Rubella, Herpes simplex, Influenza	Brown, 2005 Yolken, 2004
Maternal poliovirus infection during second trimester of pregnancy Wikipedia	Suvisaari et al, 1999
Elevated maternal IL-8 levels during second trimester	Brown et al, 2004
Childhood meningitis	Abrahao et al, 2005
Mumps or cytomegalovirus infection in children (0-12 years)	Dalman et al, 2008 Yolken and Torrey, 2008
Herpes viral infection (HSV-1) (seropositivity in adults) Wikipedia	Prasad et al, 2007
Maternal Herpes Infection (HSV-2)	Buka et al, 2007
Seropositivity to Herpes virus HHV-6: Negative association with HSV-2 and cytomegalovirus and positive asociation with HSV-1 in various subpopulations (Adults)	Niebuhr et al, 2008
Borna disease virus (seropositivity in adults)	Terayama et al, 2003
CNS infection during childhood: particularly Coxsackie B5 virus	Rantakallio et al, 1997
Toxoplasmosis (T.Gondii) seropositivity in adults . Mayoclinic.com Toxoplasmosis information	Torrey et al, 2006 Yolken and Torrey, 2008
Measles, varicella zoster and polio (Schizophrenia births)	Torrey et al, 1988
Tick infestation and Lyme disease (Borrelia burgdorferi)(Geographical and seasonal correlation)	Fritzsche, 2002
Chlamydial infection especially C.Psittaci (PCR detection in adults)	Fellerhoff et al, 2007
Lactate dehydogenase virus (Brain antigen post-mortem)	Dvorakova et al, 1990
Leptospirosis (Weil's disease): adult infection	Semiz et al, 2005
Rhesus incompatibility	Hollister et al, 1996
Winter birth	Bembeneck, 2005
Cannabis use	Boydell et al, 2006
Urbanicity	Krabbendam and Van Os, 2005
Lead exposure	Opler and Susser, 2005
Pre-eclampsia and obstetric complications	Dalman et al, 1999
Cat ownership (between ages 1-13) Viral zoonoses	Torrey et al, 2000
Inverse association with rheumatoid arthritis	Gorwood et al, 2004 Torrey and Yolken 2005
Childhood Trauma	Morgan and Fisher, 2007
Autoimmune disease prior to onset: Thyrotoxicosis, celiac disease, acquired hemolytic anemia, interstitial cystitis, and Sjogren's syndrome	Eaton et al, 2006
Postnatal Vitamin D associated with reduced risk.	McGrath et al, 2004
Inverse association with Type 1 diabetes Wikipedia	Juvonen at al, 2007
Comorbidity with Type II diabetes Wikipedia	Bellivier, 2005
High plasma homocysteine levels	Haidemenos et al, 2007
Low maternal folate and high homocysteine plasma levels	Picker and Coyle, 2005
Increased incidence of antibodies reactive to gag encoded proteins of Mason-Pfizer monkey virus (MPMV), baboon endogenous virus (BaEV) and simian retrovirus type 5 (SRV-5) in sera of first episode adult schizophrenics.	Lillehoj et al, 2000
EPIGENETIC PHENOMENA Wikipedia
Hypomethylation of leukocyte DNA in males	Shimabukuro et al, 2006
Hypermethylation of the Reelin promoter (cortex)	Grayson et al, 2005
Hypomethylation of membrane bound COMT promoter (Frontal cortex)	Abdolmaleky et al, 2006

Last update: May 8, 2008