Lifestyle

Early stress linked to depression

November 27, 2009 Edition 1

GROWING up in a stressful environment is not conducive

to becoming a well-adjusted adult.

Studies have shown that people who were constantly stressed out during childhood have an increased risk of being depressed. How exactly are the two related? Stress at a young age permanently alters the expression of a key gene in the brain, leading to a lifetime of elevated levels of a hormone that contributes to depression, according to study findings published this week by the journal Nature Neuroscience.

To figure this out, a team of German researchers stressed out baby mice by separating them from their mothers for three hours a day during their first 10 days of life. Other mice were kept with their mothers continuously, as controls. All the animals had blood tests

at six weeks, at three months and at one year.

The mice that had been separated from their mothers

had higher levels of the stress-related hormone corticosterone circulating in their blood than their counterparts, the researchers found. When the animals were subjected to stressful situations, the traumatised mice also produced more corticosterone than the controls. The researchers, at the Max Planck Institute of Psychiatry in Munich, found behavioural deficits in the stressed-out mice, too.

They were more likely to freeze up in forced swim tests and had memory problems with certain tasks. The researchers traced these problems to decreased methylation of a key section of the AVP gene, which caused the mice to make too much of the hormone

arginine vasopressin.

To confirm that arginine vasopressin was responsible for the stress, the researchers gave the mice a drug that blocked the hormone’s effects in the brain. When the drug was working, the stressed-out mice produced normal levels of corticosterone. “Our results suggest that

adverse events in early life can leave persistent marks on specific genes that may prime susceptibility to neuroendocrine and behavioural dysfunction,” they concluded. – Los Angeles Times