Depression-Like Behavioral Phenotypes by Social and Social Plus Visual Isolation in the Adult Female Macaca fascicularis

Major depressive disorder (MDD) is a debilitating psychiatric mood disorder that affects millions of individuals globally. Our understanding of the biological basis of MDD is poor, and current treatments are ineffective in a significant proportion of cases. This current situation may relate to the dominant rodent animal models of depression, which possess translational limitations due to limited homologies with humans. Therefore, a more homologous primate model of depression is needed to advance investigation into the pathophysiological mechanisms underlying depression and to conduct pre-clinical therapeutic trials. Here, we report two convenient methods--social isolation and social plus visual isolation--which can be applied to construct a non-human primate model of depression in the adult female cynomolgus monkey (Macaca fascicularis). Both social and social plus visual isolation were shown to be effective in inducing depression-like behavior by significantly reducing socially dominant aggressive conflict behavior, communicative behavior, sexual behavior, and parental behavior. The addition of visual isolation produced more profound behavioral changes than social isolation alone by further reducing parental behavior and sexual behavior. Thus, the degree of behavioral pathology may be manipulated by the degree of isolation. These methods can be applied to construct a non-human primate model of depression in order to assess physiological, behavioral, and social phenomena in a controlled laboratory setting.