Children who are anxious may have inherited the trait from their parents, a new study finds. Researchers University of Wisconsin-Madison's Department of Psychiatry and the Health Emotions Research Institute revealed how an "over-active brain circuit," which involves three areas of the brain genetically passed on, can contribute to the development of mood disorders like depression and anxiety.

The study, to be published in the Proceedings of the National Academy of Sciences this week, is based on brain scan images and involves almost 600 juvenile rhesus monkeys.

The monkeys were exposed to "mildly stressful" conditions which a child would likely be in--for instance, being placed in a room with strangers, according to Ned Kalin, a psychiatrist at the university and senior author of the study.

Kalin and colleagues then studied brain scan images of the monkeys through PET scanning and discovered that three regions in the brain attributed to anxiety were also linked to heritability.

The monkeys were raised in pairs at the Wisconsin National Primate Research Center. And since researchers know how the test monkeys are related to each other, they managed to trace the inheritance of the behaviors by looking at the family tree.

"Over-activity of these three brain regions are inherited brain alterations that are directly linked to the later life risk to develop anxiety and depression,'' said Kalin, according to the university's statement.

With results from the brain scans, researchers found that around 35% of a variety of anxiety-like behaviors could be explained by genetic history.

"Now that we know where to look, we can develop a better understanding of the molecular alterations that give rise to anxiety-related brain function,'' said Kalin.

Kalin adds that the findings provide a major step towards "understanding the neural underpinnings of inherited anxiety," which will provide "more selective targets for treatment."