Adults and teenagers with depression don't respond to rewards in a normal manner. Although depression has been diagnosed in children as young as 3, it hasn't been clear whether their responses to rewards also may be blunted. So researchers studied kids ages 4 to 7 and found that, like adults, when the children were depressed, their brains were less likely to respond to rewards. The researchers say insensitivity to rewards may serve as a "red flag" for depression in young children.