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Stress is linked to depression

A new study on mice has found that long-term exposure to stress hormone directly results in anxiety that often comes with depression, thus providing evidence that stress is linked to depression.

The study, by Neuroscientists Paul Ardayfio, PhD candidate, and Kwang-Soo Kim, PhD, at Harvard Medical School and its affiliate Mclean Hospital, was carried out on 58 mice by exposing them to both short-term and long-term durations of corticosterone, the stress hormone in rodents.

As part of the study, mice were exposed to chronic doses of the stress hormone, in which they underwent 17 to 18 days of exposure; as well as acute doses in which they underwent 24 hours of exposure.

The researchers found that when compared with mice given stress hormone for a day, mice given stress hormone for more than two weeks were not only more fearful and were less willing to explore a new environment, but it also dulled reactions to a startling stimulus, another sign that their nervous systems were overwhelmed.

The researchers say the study shows that in people, exposure to stress hormone cortisol can cause anxiety, which appears with depression.

"Our results suggest that chronically high levels of cortisol, which occurs in Cushing's disease and some subtypes of depression, can increase anxiety on the one hand and dull responses to external stimuli on the other," they said.

They added that while very-short-term or acute exposure may be adaptive, chronic exposure has detrimental effects on brain and behaviour. — ANI

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