How does the stress of witnessing community violence—seeing beatings, shootings, drug use, and so on—affect a child’s growing brain? In a pilot study, psychologist Darby Saxbe and her team took a look at long-term effects on the brain, and found that certain structures—notably, the hippocampus and the amygdala—were smaller in 17-year-olds who had witnessed community violence when they were younger.

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