The scientists found that depressed female monkeys become socially withdrawn and have reduced body fat, low levels of activity, high heart rates and disruptions in hormone levels – all of which are known or suspected characteristics of major depression in women. Their research is based on female monkeys because women are 66 percent more likely than men to experience depression during their lifetimes.
"We believe these monkeys can be a useful model for learning more about depression in women," said Carol Shively, Ph.D., professor of pathology at Wake Forest Baptist. "Current ways to treat depression are only partially successful. This may be an important opportunity to develop and test new treatments."
She said that with current treatments, there's often a difference between men and women in effectiveness and side effects. The animal model will allow scientists to evaluate the effectiveness of treatment specifically in females, the population at greatest risk.
The study involved 36 adult female cynomolgus monkeys, who normally live in social groups in the wild. For most of the research, the animals lived in groups of four and their social interactions and behavior were observed. Depressive behavior included a slumped or collapsed body posture accompanied by a lack of response to events or objects in the environment in which other monkeys were interested.
The researchers found that the depressed monkeys had suppressed ovarian function, but continued to have menstrual periods. Irregular ovulation can lead to low estrogen levels, which have been associated in both women and monkeys with increased risk of disease in the arteries leading to the heart.