Newly minted grown-ups are carrying out a massive natural experiment by choosing to do without the drugs that profoundly affected their experience of childhood. ...American society remains deeply ambivalent about the diagnosis of ADD, a catch-all term used more commonly in the past that includes today's more well-known attention-deficit hyperactivity disorder. (Children diagnosed with ADD typically have difficulty focusing and paying attention. Those with ADHD are physically frenetic as well.) Almost three decades after the psychiatric profession first detailed the condition in its diagnostic manual, nagging questions remain: Does medicating a child with ADD help that child's well-being in the...