Interaction between rhCRH genotype (C/C vs. C/T) and early rearing history (MR, mother-reared, vs. PR, peer-reared) on ACTH and cortisol responses to stress. Peer-reared T allele carriers exhibited higher plasma levels of ACTH and cortisol (mean percent change + SEM, MR C/C = 100, MR C/T = 4, PR C/C = 42, PR C/T = 3). ***, P < 0.0001; **, P < 0.01.