Chronic stress blocks a gene that protects the brain from mood disorders, according to a new study that may provide novel insights into the mechanisms behind depression, anxiety, and bipolar disorder.

The study, published in the Proceedings of the National Academy of Sciences, found that chronic stress can create brain changes associated with mood disorders by blocking a gene called neuritin in rats.

A team of scientists from Yale University studied how rats reacted to chronic, unpredictable stress by subjecting laboratory rodents to food and play deprivation, isolating them from other rats and switching around their dark and light cycles for three weeks.

Researchers found that afterwards the rats had little interest in food, enjoyed sweetened drinks, and didn't swim when placed in water, which were all signs of rodent depression.

Researchers then looked at the rats' genetic activity and found that the neuritin gene, which is also present in humans, became significantly less active compared to rats in the control group.

More importantly, scientists observed that while the rats in the stress group quickly recovered after being treated with antidepressants, rodent depression improved just as well when the rats were injected with a virus that promoted neuritin gene expression and protected the rats from brain cell atrophy and other structural brain changes associated with mood disorders, even when the rats were exposed to stress-inducing environments.

"Neuritin produced a response that looked exactly like an antidepressant," said researcher Ronald Duman, a neurobiologist at Yale University, according to Science Magazine. "I was surprised to find this molecule was sufficient, by itself, to block the effects of stress and depression."

To confirm their findings that neuritin can protect the brain from depression, researchers blocked the activity of the gene in another group of rats that did were not put in stressful environments and found that the rodents exhibited the same depression symptoms of the rats in the stressed group.

Researchers said that the results support past findings that implicate stress in the development and advancement of mood disorders, and may also offer a new therapeutic target for treating mood disorders like depression.

Previous postmortem studies and brain scans have shown that the brain's hippocampus that responsible for memory can shrink and atrophy in patients with a history of mood disorders and patients who live with these disorders have also been found to have lower levels of brain-derived neurotrophic factor (BDNF), a crucial growth factor that maintains the health of neurons.

Past findings have also suggested that low neuritin gene expression, which codes for another protein of the same name, may also protect the brain's ability to reorganize and change in response to new experiences.

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