Research — 25 May 2016

Scientists have tracked how poverty leaves its signature on young people’s genes, predisposing them to a life of depression.

In a case of nurture influencing nature, US neuroscientists have traced the biological processes that can send young people from disadvantaged neighbourhoods spiralling into mental illness.

The study, published this morning in the journal Molecular Psychiatry, is the latest to find that environmental factors can affect the operation of genes linked to depression.

“It may be surprising to learn that our environments can affect us as deeply as the level of markers on our DNA,” said first ­author Johnna Swartz, of Duke University in North Carolina. “(But) this idea is consistent with our growing understanding that our biology is not set in stone.”

The researchers combined genetics, brain imaging and behavioural analyses to investigate the effects of chemical markers on young people’s genes. These “epigenetic” tags change the way genes behave, without altering their underlying genetic codes.

In a study lasting over three years, the team tracked more than 130 young people aged ­between 11 and 15.

It found that those growing up in disadvantaged households accumulated more epigenetic tags near a gene called SLC6A4, which help controls levels of the neurochemical serotonin.

MRI brain scans revealed that more tags corresponded with a more active amygdala — a brain region that co-ordinates ­reactions to threat — when participants looked at photographs of fearful faces. Those with more active amygdalae later proved more likely to report symptoms of depression.

“This is some of the first research demonstrating that low socio-economic status can lead to changes in the way genes are expressed,” Dr Swartz said.

Prior studies have shown that poverty could affect the ­expression of other genes associated with depression, she told The Australian.

But the new research was the first to track how these changes affected brain development and triggered depressive symptoms.

Dr Swartz said deprived upbringings could involve “chronic stressors” such as family discord, poor nutrition and smoking.

“These small daily hassles of scraping by are evident in changes that build up and affect children’s development.”

The team is scouring the ­genome looking for other markers linked to depression. The aim is to develop diagnostic tests capable of predicting risk at the individual level.

“Understanding the biological pathways involved for an ­individual may help us predict the course of the disorder, or how that individual will respond to different treatments,” Dr Swartz said.

This article first appeared on ‘The Australian’ on 25 May 2016.

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