Does the thought of being late to a meeting make your pulse race? Does setting foot in a crowded shopping center make your palms clammy? Do you start to sweat if you think you left your phone at home? If you find yourself experiencing stress in these sorts of situations, then it might be inherited genes that are to blame.

A team of researchers, from the University of Wisconsin-Madison, has already shown that an anxious temperament is a trait that can be inherited. Now they've continued their research to map regions of the brain that express anxiety in rhesus monkeys and see if they show signs of inherited anxiety. The research on rhesus monkeys is an important, translatable tool in understanding what causes depression and anxiety in human children, and if left untreated can lead to other mental illnesses later in life. Dr. Ned Kalin, the senior author of the study published in the Proceedings of the National Academy of Sciences, explained to IFLScience that "What we've done, basically, is establish a way to model the early risk that children have in rhesus monkeys." 

During the study they found that a strong and overactive connection between three areas of the brain could be linked to inherited anxious behavior. The identified regions of the brain responsible for a stressed-out state were the prefrontal cortex (near the forehead), the limbic system and the midbrain (both in the center of the brain). This conclusion came from a study of nearly 600 rhesus monkeys.

In order to create this brain-map that correlates to anxiety, the team gave the monkeys a marker that built up in regions of the brain that received the highest blood flow. The monkey was then exposed to a situation that a human child would find mildly stressful. Dr Karin described the experiment. "We exposed them to a stranger for 30 minutes and during the time the material that we give them gets taken up into their brain. It gets locked into brain regions that are more active during that experience of being exposed to someone that might be anxiety-provoking."

Then the monkeys received a positron emission tomography (PET) scan so that the team could measure where the tracer was taken up in the brain and in what quantity. These results were then compared to how the monkey physically reacted while being exposed to the stranger: whether they were very anxious, not at all anxious or somewhere in the middle. This effectively created a map that identified regions in the brain associated with anxiety.

The next step was to determine which components of anxiety the monkeys inherited from their parents and which were environmental anxiety. The team looked at the individual level of anxiety that each monkey had and then examined how this correlated to the anxiety expressed in their relatives. The brain regions thought to be inherited expressed the exact same patterns of anxiety markers in the brain. Dr Kalin concluded, "What we found was that roughly 30% of your likelihood of developing anxiety in inherited."

This is a significant result. "Roughly a third of the risk is related to what is passed down from your parents and grandparents to you. We've always known that these complex disorders have multiple underpinnings, including genetic, as well as environmental experience."

These findings will assist future understanding of inherited brain alterations that exhibit anxiety not just in monkeys but in human children, and how this affects the development of anxiety and depression later in life.