Also, some cross-sectional studies have investigated DNA methylation in specific genes (e,g; BDNF and MB-COMT) in individuals with different psychiatric disorders17,18,66 and their data suggested higher DNA methylation in individuals with internalizing disorders and decreased DNA methylation in patients diagnosed with schizophrenia and bipolar in comparison to subjects without psychiatric disorders. This evidence concerns the gene BDNF and internalizing disorder.