A method for diagnosing or giving a prognosis for anxious temperament or trait-like anxiety in a human or non-human primate subject comprising the steps of (a) obtaining DNA from a blood or saliva sample from the subject and (b) quantifying methylation in a set of differentially methylated regions (DMRs) selected from SEQ ID NOs:1-75 or DMR-associated genes selected from DIP2C, GRB10, INPP5A, C17ORF97, PDXK, CACNA2D4, TRAPPC9, CRTC1, MEGF6, HIVEP3, OPCML, PITPNM2, ZFPM1, RAP1GAP2, NFATC1, RNF126, FSTL3, GNAS, SH3BP2, NEURL1B, MAD1L1, HSPA12B, IGF2, PEG10, PEG3, SLC16A3, SYTL1, and ZIM2, wherein a significant change methylation indicates the present of anxious temperament or trait-like anxiety, wherein the change is relative to DNA from a second human or non-human primate who does not have anxious temperament or trait-like anxiety. Also disclosed is a biomarker panel of DMR and DMR-associated genes for the diagnosis or prognosis of anxious temperament or trait-like anxiety.