It’s long been known that growing up in stressful environments is bad for kids. But the degree to which poverty and instability affect children is tempered by their specific genetic makeup, according to a study by ISR researcher Colter Mitchell. Mitchell and colleagues studied a group of 40 African-American nine-year-old boys, half from nurturing environments and half from harsh home environments, using telomeres as markers of stress, according to an April 9 article in The Newcastle Star. (Telomeres protect the ends of chromosomes from deterioration and generally shorten with age, disease, or stress.) The study showed that environment affected all the boys—with good conditions leading to longer telomeres and bad causing them to shorten. But boys with heightened sensitivity in the serotonin and dopamine genetic pathways had both the shortest and the longest telomeres. “Our findings suggest that an individual’s genetic architecture moderates the magnitude of the response to external stimuli—but it is the environment that determines the direction,” Mitchell says.