Parents of teenagers worry about lots of things: drugs, se*, poor choices of friends. But the activity that causes the most harm to older teenagers is none of the above.

• 青少年家长担忧他们的孩子们很多事情：毒品，性，滥交朋友。但是最伤害那些年纪稍长点的青少年的却不是以上任何一件事情。