Background: Evidence suggests that childhood is an important critical period for adult mental health outcomes. Most studies evaluating childhood factors use cross-sectional data, limiting our understanding of life course factors contributing to mental health. The purpose of this study was to evaluate the contribution of life course factors on adult mental health treatment from a longitudinal cohort of U.S. respondents. Methods: We used data from the National Longitudinal Survey of Youth-1997 (N=8,984) through the 2011 data collection year, in which n=7,009 adult respondents reported on the number of mental health visits between 2009-2011. We used zero-inflated negative binomial regression to evaluate the impact of childhood, adolescent, and adult factors on mental health visits. Results: Respondents with more than three adverse childhood experiences (ACE) reported in adolescence were significantly more likely to utilize mental health treatment as an adult (Incidence Rate Ratio[IRR]=1.30). No other childhood or adolescent factors contributed to adult mental health utilization. Adult factors associated with greater mental health visits included: having any health insurance (IRR=1.40), being unemployed (IRR=1.56) or employed part-time (IRR=1.31). African-American respondents had significantly fewer mental health visits than white respondents (IRR=0.79). Non-significant factors included: gender, ethnicity, parent-reported childhood emotional problem, family receipt of governmental assistance as an adolescent, living in a high-poverty household as an adult, and living in a state with high unemployment. Conclusions: Critical periods of development, combined with cumulative risk and protective factors, contribute to adult mental health seeking. Adolescence is a critical period for trauma and later need for mental health treatment. Other factors, such as full-time employment, appear to be associated with reduced likelihood of the need for mental health treatment. Future evaluation of community and population-based approaches, including policy interventions, is needed to understand risk and protective factors contributing to mental health across the life course.