Living in poverty can cause changes to people’s DNA that make them more likely to become depressed, anxious and possibly take drugs, according to a ground-breaking new study.

Researchers in the United States found that teenagers from deprived backgrounds tended to undergo changes to a gene that increases the activity of a part of the brain involved in the ‘fight or flight’ response and panic attacks. This increased activity in the amygdala has been linked to a greater risk of depression.

They also found that a low socio-economic status was associated with low levels of serotonin, sometimes referred to as the happiness hormone.

In recent years, studies have shown that not only can genes be changed by the environment and even social interactions, but these ‘epigenetic’ changes can then be passed on to the next generation.

In a new paper in the journal, Molecular Psychiatry, scientists from Duke University in the US described how this might help explain why depression appears to run in some of the poorest families.

Deprivation was associated with “a host of negative outcomes including poorer general health and increased risk for mental illness including depression, anxiety, and addiction”, they wrote.

“Low socio-economic status may confer risk through a variety of mechanisms, including higher levels of perceived and objective stress and cumulative environmental risk such as poor housing quality, noise pollution, and exposure to violence,” the researchers added.

The study’s lead researcher, Dr Johnna Swartz, said their work had shown how these kinds of problems were affecting the genes of the people concerned.

“This is some of the first research to demonstrating that low socio-economic status can lead to changes in the way genes are expressed, and it maps this out through brain development to the future experience of depression symptoms,” she said.

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

They studied changes involving a specific gene, called SLC6A4, in 132 adolescents aged between 11 and 15 over a period of two years.

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People from poor backgrounds were found to accumulate greater quantities of a chemical tag on or near the gene that made their amygdala more responsive to photographs of fearful faces that were shown to then while their brain was being monitoring by an MRI scanner.

Study co-author Professor Douglas Williamson said: “The biggest risk factor we have currently for depression is a family history of the disorder.

“Our new work reveals one of the mechanisms by which such familial risk may be manifested or expressed in a particular group of vulnerable individuals during adolescence.”

And Ahmad Hariri, a Duke professor of psychology and neuroscience, added: "As they enter into young adulthood they are going to be experiencing more problems with depression or anxiety - or maybe substance abuse.