As a doctor who works in a pediatric intensive care unit, I take care of a lot of extremely sick children. Typically, when a patient is memorable, it is because they have unusual symptoms or a rare illness or injury. But lately there have been several patients who haunt me because of their similarity. Over the last decade of my career, I have seen a dramatic increase in children and teens who try to harm themselves. They have the same haunted look, the same worried parents, the same palpable sense of despair. I have seen children as young as 9 try to kill themselves. Suicide is the second-lead…