Maggie's Farm

Dr. Friedman blames it on the hormones and slow brain maturation: Why Teenagers Act Crazy:

... most adolescents do not develop anxiety disorders, but acquire the skill to modulate their fear as their prefrontal cortex matures in young adulthood, at around age 25. But up to 20 percent of adolescents in the United States experience a diagnosable anxiety disorder, like generalized anxiety or panic attacks, probably resulting from a mix of genetic factors and environmental influences. The prevalence of anxiety disorders and risky behavior (both of which reflect this developmental disjunction in the brain) have been relatively steady, which suggests to me that the biological contribution is very significant.