PROJECT SUMMARY Drug overdose is now a leading cause of death among U.S. adolescents, with mortality increasing in recent years with the proliferation and involvement of illicitly manufactured fentanyl (IMF). In parallel, nonfatal adolescent drug overdoses treated in emergency department (ED) settings have also increased. In contrast to fatal overdoses, nonfatal overdoses mainly involve non-opioid drugs, including psychostimulant and other psychotropic drugs that adolescents may use with a prescription or misuse from illicit sources with high risk of IMF adulteration. To reduce morbidity and mortality from adolescent drug overdose, we need to better understand the epidemiology of specific drug involvement in nonfatal overdoses, focusing on drugs commonly containing IMF. Overdoses treated in acute care (ED) settings represent critical opportunities for risk assessment and intervention, as mortality is significantly elevated in the period after a nonfatal event. However, limited research suggests that receipt of comprehensive behavioral health care after overdose is exceedingly low in adolescents, related to the lack of pharmacological treatments for substance use disorders, limited access to developmentally appropriate behavioral therapies, and high rates of co-occurring mental illness and suicide symptoms that complicate treatment decisions. Thus, we need to address the large gaps in evidence on the type and timing of treatment adolescents receive following a nonfatal overdose and understand the relationship between follow-up care and risk of repeat overdose. To generate evidence that can be used to inform effective prevention and treatment strategies, this proposal’s overall goal is to identify individual and clinical care factors associated with adolescent overdose risk. The specific aims are to: (1) estimate the prevalence of adolescent nonfatal drug overdose and identify high-risk demographic and clinical subgroups, stratifying by drug involvement (e.g., fentanyl) and overdose intent; (2) examine receipt of behavioral health treatment (type, timing) after nonfatal drug overdose and variation in treatment receipt by demographic and clinical characteristics; and (3) estimate incidence, critical high-risk periods, and risk factors for repeat overdoses, including the relationship with behavioral health care received after the initial event. Our central hypothesis is that drug overdose patterns differ by adolescent characteristics (e.g., sex, age group, mental health diagnoses) and that follow-up care is limited but impacts the risk of repeat overdoses. To achieve these goals, the study team will leverage national longitudinal Medicaid claims data (2016-2022) comprising over 400,000 overdose events in adolescents aged 12-18 years. Our proposal offers a valid and timely approach to yield novel, generalizable, and up-to-date evidence on overdose risk and treatment in a vulnerable adolescent population. Findings will generate actionable estimates to ...