Project Summary In the early 2000s, an estimated 1% of United States youth received antipsychotic prescriptions. Of these prescriptions, approximately 65% were given for non-FDA-approved indications. This led to urgent calls to curb antipsychotic prescribing, based on both the lack of research on drug benefits in youth and the extensive evidence demonstrating adverse metabolic and neurologic consequences. More than a decade later, the characteristics of the current pediatric population receiving antipsychotics, and the degree to which these medications alleviate psychological symptoms, remain unclear. The objective of this proposal is to understand the pediatric population receiving antipsychotics and examine their effectiveness in reducing psychiatric hospitalizations compared to alternate medication options. It will use a new-user patient sample (N = 46,425) that is large enough to adequately study hospitalization risk and examine differential effects based on demographic factors and conditions that have scarcely been studied (e.g., depression), yet appear frequently in antipsychotic users. This project will use a large United States health claims dataset to accomplish this objective through two specific aims: (1) characterize the youth population using antipsychotics by examining individual factors that predict antipsychotic initiation and (2) contrast medication effectiveness at reducing rates of psychiatric hospitalizations using active comparator designs. In Aim 1, antipsychotic users (cases) will be matched 1:1 with non-users (controls). The odds of using antipsychotics will then be evaluated based on pre- existing psychiatric diagnoses, race, and socioeconomic status. In Aim 2, survival analysis will be used to compare rates of psychiatric hospitalizations across different comparisons. First, differences in rates of psychiatric hospitalizations will be compared for aripiprazole and risperidone users both across the sample and in demographic subgroups. Second, rates of hospitalizations will be contrasted for antipsychotics versus ADHD stimulants in users with ADHD and antipsychotics versus antidepressants in users with depression. The active comparator design and propensity score matching will be applied to ameliorate confounding by indication and related factors that obscure the ability to identify causal effects of the medications. This work is innovative as it will provide insight into comparative effectiveness of antipsychotics and alternative treatment options for pediatric conditions (e.g., ADHD) that have rarely been studied. Furthermore, the results will have a significant public health impact by providing greater insight on disparities in antipsychotic treatment and how antipsychotics may differentially affect diverse populations. This program of research will dovetail with the applicant’s prior experience on causal inference methods and their long-term goal of becoming an impactful pharmacoepidemiologist by training the applicant...