If your teenager seems even more ornery than usual, you may want to consider restricting the time he or she spends online. That’s based on data from Kaohsiung University in Taiwan, where researchers have found a link between aggression in teens and heavy Internet use. Of the group of 9,400 study subjects classified as Internet addicts (25% of the boys and 13% of the girls), some 37% — a significant jump from the overall average — reported threatening or harming others over the past year. The study appears in the online version of the Journal of Adolescent Health.