We examined trends in depression among 17-year-olds to understand the contribution of incoming students to the demand for collegiate mental health services. Seventeen-year-olds (N = 32,325) from the National Surveys on Drug Use and Health (NSDUH) for 2008 to 2019 were included. The proportion of 17-year-olds reporting depression during their lifetime, during the past year, or for the first time in the past year were determined for each year. Rates of depression remained similar from 2008 to 2012 (lifetime, 17%; current year, 11%; incident cases, 5%) followed by the onset of a significantly growing wave, almost doubling by 2019, reaching 30% (lifetime), 21% (current year) and 9% (incident cases). This wave shows that depression emerges before college for a high proportion of youth. Collegiate mental health must focus on this wave among arriving students, in addition to programs for the much smaller new incidence of depression that emerges during college.