This study was undertaken to analyze DNA methylation profiling at the monoamine 
oxidase A (MAOA) locus, in order to determine whether abnormal DNA methylation 
is involved in the development of schizophrenia. We recruited a total of 371 
patients with paranoid schizophrenia (199 males and 172 females) and 288 
unrelated control subjects (123 males and 165 females) for analysis of DNA 
methylation. Diagnosis was made based on the Structured Clinical Interview for 
DSM-VI. Genomic DNA extracted from peripheral blood was chemically modified 
using bisulfite, and DNA methylation profiles of the MAOA promoter were 
determined by BSP-sequencing. DNA methylation ratios of individual CpG residues 
and overall methylation ratios were measured on each subject. The results showed 
that there was no significant difference in overall DNA methylation ratios 
between patients and controls either in the female group (P = 0.42) or in the 
male group (P = 0.24). Of 15 CpG residues that showed significant differences in 
DNA methylation status between the patient group and the control group in 
females, eight of which had an increased level and seven, a decreased level, 
with a combined P value of 1 (df = 160). In male subjects, however, six 
individual CpG residues showed an increased methylation level with a combined P 
value of 5.80E-35 (df = 158). In conclusion, abnormalities of DNA methylation at 
the MAOA promoter may be associated with schizophrenia in males.