A group of female cynomolgus monkeys in Winston-Salem, N.C., are poised to offer valuable new information about depression in humans—particularly in women, who account for nearly 12 million of the 19 million cases diagnosed each year in the United States. The study of these monkeys, led by Carol Shively, professor of pathology at the Wake Forest University School of Medicine, introduces the first primate model of adult depression.
Animal studies of depression have labored under several drawbacks. The standard model has been the rodent, whose brain lacks the complex neural circuitry that underlies mood and emotion in the human brain; moreover, the study populations have been almost exclusively male. In addition, although rodents live in groups in the wild, in the laboratory they have usually been housed in social isolation, one to a cage. Finally, the stimuli commonly used to produce stress (such as a movement-constraining harness or the administration of small electric shocks to the foot) do not correspond well with sources of stress in the animals’ natural setting.
As they explain in the April Journal of Biological Psychology, Shively and colleagues have broken with tradition by developing a primate rather than a rodent model for depression, by using only females in their study population, and by focusing on “social stress”—that is, the day-to-day demands, rebuffs, and shifting alliances of a typical community.
The researchers have established that the chronic stresses of life in a social group can indeed bring on depression in susceptible individuals. At the same time, they have developed an animal model that may permit more accurate testing of possible new treatments for depression. Next, Shively says, “We will be looking inside the monkeys’ brains with PET imaging, perhaps even getting pictures of some antidepressant treatments at work.”