Psychotherapy such as cognitive behavior therapy are beneficial in some patients, but not in others. Clearly, individual factors play roles in the pathogenesis, development, and treatment response of mental disorders. Genetic factors are involved in such variations. Epigenetic regulation, for instance through DNA methylation and histone acetylation, is one of the essential factors in the control of gene expression. To date, it has been shown that DNA methylation and histone acetylation are dynamically regulated in the adult nervous system. In particular, several studies have shown that the alteration of DNA methylation is involved in the pathology of mental TH-302 disorders such as depression and anxiety disorders, and cognitive functions such as memory formation. Many twin studies have revealed that the onsets of various diseases including psychiatric disorders are not the same in monozygotic twins. In addition, there is a report that although twins are epigenetically indistinguishable during the early years of life, older monozygous twins exhibit remarkable differences in their overall content and genomic distribution of 5methylcytosine DNA and histone acetylation. These studies suggest that the growth environment after birth affects development of various diseases through the mediation of epigenetic changes. B-vitamin folate, methionine and choline are essential for onecarbon transfer reactions including DNA methylation, which regulates the transfer of methyl groups in biological methylation reactions; these nutrients work as methyl donors. Deprivation of methyl donors such as Vitamin B and choline during pregnancy in rats has been revealed to affect the pups’ internal organs such as the gastric mucosa. Rat pups from dams fed diets lacking methyl donors showed long-lasting disabilities in exploratory behavior and learning and memory capacities, and reduction of the thickness of the CA1 pyramidal layer in the hippocampus along with spatial memory impairment. Importantly, a previous study revealed that the long-term reduction of dietary methyl donors after weaning induced alteration of epigenetic status in the rat brain, although its effect on behavior was not investigated. In addition, a previous study of the postmortem human hippocampus showed that the methylation state was different in suicide victims with child abuse from those without child abuse; thus, epigenetic alteration in specific genes during early childhood potentially contributes to the later development of mental disorders. Given this background, we aimed to investigate the potential effect of epigenetic rearrangement during the maturing brain on the future development of fear and anxiety. Taken together, these findings indicate that the growth environment during the postnatal developmental period affects DNA methylation-associated factors and that the altered status of DNA methylation can be reversed by appropriate treatment thereafter. Behavioral tests revealed that the fear response and anxiety behavior were affected in both the FMCD and food-restriction groups, but the alterations were different between the two groups. A marked difference appeared in the results of fear conditioning in juvenile mice exposed to the two types of food restriction for 3 weeks.