Many families experienced financial hardships during the Great Recession, with stress and anxiety were undoubtedly rampant in some families. But researchers have found that mothers, at least, channeled their stress into their children, treating them more harshly — by shouting, spanking, and threatening them — even if they weren't directly affected by the recession themselves. The reason, they say, is in the mothers' genes.

The DRD2 gene, also known as the "orchid/dandelion gene," controls the release of dopamine — a hormone that regulates behavior — and is sensitive to its environment. It has also been associated with aggressive behavior. About half of the population has the gene, and in less stressful conditions, people are less likely to be aggressive with their kids. During the recession, there has been a documented growth in the number of reported parental abuse, and parents who had the gene were found to be almost exclusively responsible, according to US News & World Report. Only mothers were included in the study.

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"You have the same genes, and with a different environment it's a completely different story," Irwin Garfinkel, professor of contemporary urban problems at Columbia University, told NPR. "I think that's the most amazing part of what we found."

Garfinkel wasn't looking for this link when he began his study. Instead he was working on the Fragile Families and Child Wellbeing Study, which tracked almost 5,000 children living in 20 cities around the country born between 1998 and 2000. But when they noticed that reports of harsh parenting rose at the beginning of the recession in 2007, and then fell as the recession got worse, Garfinkel's team began to investigate. Based on interviews conducted when children were 1, 3, 5, and 9 years old, researchers found that a 10 percent increase in unemployment was linked to a 16 percent increase in harsh maternal parenting.

Most mothers with the gene were more likely to abuse their children simply because they had become fearful of losing their job.

"It was the general economic condition. If you remember the papers back in 2008, newspapers said we were on the way to a great depression and policy makers were scared," Garfinkel said. "It was during that period that harsh parenting increased the most."

The orchid/dandelion theory is well known among geneticists and derives its name from the plants' responses to stress. Garfinkel says that while dandelions tend to do well regardless of weather conditions, orchids die in poor conditions and thrive in good environments.

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"The same gene that makes you look vulnerable in a bad situation makes you do better in a good environment. In a good environment, an orchid flourishes and is beautiful," he says. "But some of us, we're dandelions — we might not thrive, but we can survive in all environments."

Source: Lee D, Garfinkel I, Notterman D, et al. The Great Recession, genetic sensitivity, and maternal harsh parenting. PNAS. 2013.