Study Report

Reference	Kunugi, H., 1998 PMID: 9774778
Citation	Kunugi, H., R. Fukuda, et al. (1998). "C677T polymorphism in methylenetetrahydrofolate reductase gene and psychoses." Mol Psychiatry 3(5): 435-437.
Disease Type	Bipolar Disorder & Schizophrenia
Study Design	case-control
Study Type	Candidate-gene association study
Sample Size	343 patients with schizophrenia, 143 with bipolar disorder, 71 unipolar major depression and 258 controls
SNP/Region/Marker Size	1 polymorphism
Predominant Ethnicity	Mongloid
Population	Japanese
Gender	167 men and 176 women with schizophrenia, 53 men and 90 women with bipolar disorder, 25 men and 46 women with unipolar disorder, 129 men and 129 women controls
Age Group	adults : The mean age (standard deviation; s.d.) was 42.2 (12.8) for the schizophrenics, 47.9 (13.6) for the patients with bipolar disorder, 55.2 (14.8) for the unipolar depression, and 31.3 (11.3) for the controls.

Sample Diagnosis	DSM-IV
Sample Status	One hundred and eighty-four patients with schizophrenia were recruited from the general psychiatric clinic of Teikyo University Hospital, Tokyo, and the remaining subjects were from wards of three psychiatric hospitals around the Tokyo Metropolitan area. Patients with affective disorders were from the general psychiatric clinics of Teikyo University Hospital, Showa University Hospital, and Shiga University of Medical Science Hospital. Two hundred and seventy-nine cases (81%) of the schizophrenics, 120 (84%) of the bipolar, and 36 (51%) of the unipolar patients had a history of hospitalization. The mean age of onset was 25.0 (s.d. 8.4) years for the schizophrenics, 34.1 (12.8) for the bipolar, and 44.2 (15.3) for the unipolar patients.
Technique	PCR amplification and genotyping
Statistical Method	The presence of Hardy-Weinberg equilibrium was tested by the x2 test for goodness-of-fit. Frequency of homozygosity for the mutated type (T677) was compared between each diagnostic group and the control group by the x2 test for independence; comparisons for three diagnostic groups were made and the critical P-value of 0.017 (0.05/3) was used according to the Bonferroni's correction for multiple testing.
Result Summary	there was no significantly increased frequency of homozygosity for the T677 allele in any of the diagnostic groups, compared to the controls. Our results suggest that homozygosity for the T677 allele of the MTHFR gene is unlikely to play a major role in the pathogenesis of schizophrenia or affective disorders in our sample.