Background: The prevalence of pediatric mental health (MH) diagnosis and treatment have expanded in the U.S. We assessed the longitudinal patterns of incident diagnosis and new psychotropic medication use in a Medicaid-insured birth cohort. Additionally, continuity and quality of MH service utilization were assessed in a publicly-insured pediatric population. Quality care was defined by the 2009 Children's Health Insurance Program Reauthorization Act (CHIPRA) mandated children's health care quality measures. Methods: We applied longitudinal designs to Medicaid claims data from a Mid-Atlantic state (2007-2014). Using Kaplan-Meier estimators we assessed the cumulative incidence of MH service use in a cohort of newborns (aim 1). We assessed the association between relational patient-provider continuity of care and: 1) emergency department (ED) visits or hospitalizations in the 12 months following first MH diagnosis among 3-16 year olds (aim 2); and 2) the quality of follow-up care among 6-12 year old new users of ADHD medications (aim 3), using logistic regression models. Quality was defined as having ≥1 follow-up outpatient visit in the 30 days following medication initiation and ≥2 follow-up visits in the 270 days after the first follow-up visit, with a total medication supply of ≥210 days. Results: By age 8, 19.7% and 10.2% of the birth cohort (n=35,244) had received a MH diagnosis or psychotropic medication, respectively. Among medication users, 80.5% received monotherapy, 16.4% received 2 medication classes, and 4.3% received ≥3 medication classes concomitantly for ≥60 days. Compared to children with high CoC, the odds of ED visits was significantly higher among youths with low CoC [Odds Ratio(OR)=1.27; 95% CI=1.13-1.41] and low CoC was associated with greater odds of hospitalization [OR=1.17; 95% CI=1.06-1.29]. Compared to those with low CoC, children with higher continuity of care had greater odds of meeting CHIPRA initiation- [OR=1.41; 95% CI=1.25-1.60] and continuation-phase [OR=1.45; 95% CI=1.29-1.64] visit-based measures. Conclusions: Early exposure to psychotropic medications and prolonged duration of use have implications for long-term safety, highlighting the need for safety and outcomes research in pediatric populations. Our findings suggest a need for more research in the areas of quality assessment and continuity of care among youths with mental health conditions.