Xu F, Wu Q, Xie L, Gong W, Zhang J, Zheng P, Zhou Q, Ji Y, Wang T, Li X, Fang L, Li Q, Yang D, Li J, Melgiri ND, Shively C, Xie P. Macaques exhibit a naturally-occurring depression similar to humans. Sci Rep. 2015 Mar 18; 5:9220.