When I started using antidepressants, I didn't know anyone else my age who was taking them. Within a few years, I felt hard-pressed at times to find someone who wasn't. Antidepressants and other psychiatric medications went mainstream in the 1990s and 2000s, and my generation became the first to use these drugs in significant numbers as adolescents and young adults.

Young people are medicated even more aggressively now, and intervention often starts younger. In children, as in adults, antidepressants and medications for attention-deficit hyperactivity disorder are often used continuously for years. These trends have produced a novel but fast-growing group--young people who have known themselves longer on medication than off it.

The National Center for Health Statistics says that 5% of American 12- to 19-year-olds use antidepressants, and another 6% of the same age group use medication for ADHD--in total, about four million teenagers. Around 6% of adults aged 18 to 39 use an antidepressant. Usage often becomes long term. According to the U.S. Centers for Disease Control and Prevention, 62% of Americans aged 12 and over who take antidepressants have done so for two years or longer; 14% have taken them for 10 years or longer. Not all are well supervised. The National Center for Health Statistics reports that fewer than a third of patients of all ages who take an antidepressant have seen a mental-health professional within the past year.