Chronic stress induces epigenetic modifications in Npy and CB1 genes. Chronic stress alters Npy expression and Npy1r function in the cingulate cortex. Chronic stress alters CB1 mRNA in low CB1-expressing neurons. Reduced H3K9ac level may be responsible for impairments at molecular level. URB597 prevents the altered H3K9ac levels at the Npy gene.