Table 1.

Human signs and symptoms of depression and anxiety and their equivalent non-human primate (NHP) depression- and anxiety-like signs.

Depression and Anxiety Signs and Symptoms
Human#	Macaque	Marmosets
Lack of motivation/lack of interest*	Lack of interest in preferred foods, lack of interest in novel objects	Lack of interest in preferred foods, lack of interest in novel objects
Loss of interest in others*	Avoids others in the group, withdrawal from any approach by others, sits alone, no active social interactions	Avoids others in group, withdrawal from any approach by others, sits alone, no active social interactions
Reports of sadness*	Increased “hoo” vocalizations when iso-lated from group, lack of interest in others’ activity	Increased “phee” vocalizations when isolated from group, lack of interest in all activity
Apparent sadness in expression/posture*	Sits in self-clasping huddle position with hunched posture	Sits in hunched posture with head down, sometime with messed fur
Concentration difficulties	Difficulties with problem solving, trouble following learned tasks	Difficulties with problem solving, trouble following learned tasks
Slow movement or agitated movements	Long periods of passive sitting or rapid pacing and/or hopping	Long periods of passive sitting or constant vigilant behavior with alarm “tse” vocalizations
Agitation**	Movement stereotypies (i.e., circling in place, hair pulling, saluting, self-biting)	Constant vigilant jumping from branch to branch accompanied by “tse” vocalizations
Fear**	Vocalizations, vigilance, freezing posture	Hides in back of cage away from others
Loss of appetite	Not eating during regular feedings and ignores treats	Not eating during regular feedings and ignores treats
Sleep disturbances	Activity during sleep phase, or sleeping during day	Sleeping during times of group activity
Somatic symptoms (e.g., pain, difficulty breathing, gastrointestinal dysfunction)	Somatic signs (e.g., diarrhea, constipation, increased heart rate, altered breathing)	Somatic signs (e.g., diarrhea, increased heart rate, altered breathing, messed fur)

^#American Psychiatric Association (2013). It should be noted that although freezing and vocalization behaviors are adaptive in the defensive repertoire of NHPs, the characteristics of the response (e.g., intensity, duration) in NHPs exhibiting depression- and anxiety-like behaviors differs (e.g., : intensity, duration) from a normal response (Fox and Kalin, 2014). *corresponds to typical signs of depression; **corresponds to typical signs of anxiety. See Tables s 2–4 for detailed marmoset and rhesus specific behavior evaluations and associated citations. Icons were created with BioRender.com.