Plasma homocysteine, folate and B12 in chronic schizophrenia

Elevated plasma levels of the amino acid homocysteine have been associated with schizophrenia, particularly in young male patients. Among other factors, low folate and vitamin B12 levels have been implicated in the increase in homocysteine. In order to investigate this association, we determined plasma homocysteine, folate and B12 levels in 97 (67 males and 30 females) inpatients with chronic schizophrenia and 103 (46 males and 57 females) controls. Patients and controls did not differ in folate or B12 levels, after adjusting for age. Patients with schizophrenia had higher plasma homocysteine than controls (mean = 15.42 μmol/l in cases versus 11.54 μmol/l in controls: F(1,195) = 17.978; p < 0.001). This difference persisted after controlling for folate and B12 concentrations. Both male and female patients had increased plasma homocysteine compared to controls [(males: mean = 16.61 μmol/l in cases versus mean = 13.72 in controls: F(1,110) = 5.54; p = 0.020) (females: mean = 12.78 μmol/l in cases versus mean = 9.79 μmol/l in controls: F(1,84) = 13.54; p < 0.001)]. When dividing our sample into two age groups (age < and ≥ 50 years), both young and older females and younger males with schizophrenia had increased plasma homocysteine compared to controls. We therefore suggest that homocysteinemia is a general risk factor for schizophrenia. We further suggest that it is not limited to young male patients and is not necessarily associated with low folate or B12 levels.