1.1 billion outpatient visits by adolescents and young adults from 2006 to 2019 were associated with a mental health condition. Mental health-related diagnoses were more prevalent among visits by male versus female patients (16.8 versus 10.9 percent), with the difference most pronounced among young adults (20.1 versus 10.1 percent). From 2006 to 2019, there was an almost doubling in the proportion of mental health related visits, from 8.9 to 16.9 percent.