Anxiety and Genetics: Common Genes May Explain Anxious Behavior In Chickens, Humans and Mice

What do humans, mice and chickens have in common? A new study from Linköping University in Sweden suggests we may share common genes linked to anxiety and fear.

In the latest genetic study, researchers were interested in figuring out why domestic chickens are less anxious than their wild cousins, the red junglefowl. A genetic analysis, paired with studies in humans, identified several genes that are responsible for these behavioral differences, many of which are similar to those found in mice, according to a news release.

"By necessity, human genetic studies of behavior often focus only on susceptibility to a mental health disorder. But what about more subtle differences in behavior? For example, what makes one person a little more anxious than others? And what makes someone else a little bolder?" said Dominic Wright, study leader from Linköping University. 

So what has triggered this genetic difference between wild and tame relatives? Domestication, researchers say. After thousands of years of selective breeding, modern barnyard chickens are less anxious than their jungle-dwelling counterparts because they were genetically programmed to act that way.

For their experiment, researchers placed groups of junglefowl and domestic chickens in a "new environment." While the domestic animals explored the entire space rather calmly, the wild chickens spent their time either frozen in fear due to the unfamiliar surroundings or ran around the test arena in an erratic fashion.

This "open field test" was coupled with a genome analysis, in which researchers looked for blocks or groups of neighboring genes that are typically inherited together and highlight genome regions associated with a specific behavioral trait, such as anxiety. The specific genes of interest were those located in the hypothalamus, which is the region of the brain responsible for regulating anxiety.

Researchers found four of the genes related to anxious behavior in the chickens were also associated with those responsible for anxiety in mice, while three were associated with schizophrenia or bipolar disease previously identified in humans.  

"Though we can't yet prove these genes have equivalent functions in chicken and humans, the data certainly raises the intriguing possibility that genes controlling variation in behavior can be remarkably conserved between a whole variety of species," Wright explained in the release.  

For example, many people diagnosed with bipolar disorder also experience anxiety disorders.

"Understanding the genetics underlying the chicken results may provide fundamental insights into animal behavior, including normal behavioral variation in humans," he added.

Their findings were recently published in the journal Genetics.

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