PROJECT SUMMARY Serious mental illnesses (SMIs) including schizophrenia, bipolar disorder, and major depressive disorder disproportionately affect people who are dually eligible for Medicare and Medicaid (“dual eligibles”). The US population with SMI experiences one of the largest health disparities in the US, dying 10-20 years earlier than the overall population. Widespread undertreatment of SMI and comorbid physical health conditions, intertwined with social and economic risks (e.g., low-income, inadequate housing), is a key driver of excess mortality in SMI. Dual eligibles with SMI, with their high concentration of low-income and disability, are a particularly high- need subgroup of the overall US population with SMI. Dual Medicare-Medicaid coverage aims to facilitate access to the array of specialty mental health, general medical, and long-term services and supports (LTSS, like home-based personal care) needed by people with SMI but has fallen short of this goal. Medicare covers all general medical and most specialty mental health outpatient care, inpatient care, and prescription drugs. Medicaid covers intensive behavioral health services excluded from Medicare, like psychiatric rehabilitation and crisis response services, as well as additional inpatient psychiatric days beyond Medicare’s 190-day lifetime limit and some psychotropic medications not covered by Medicare. Medicaid also covers LTSS. Medicare and Medicaid have been poorly integrated to serve dual eligibles, leading to conflicting financial incentives, fragmented care delivery, and complicated administrative processes. Together, these issues create inefficiencies and care patterns that frequently result in sub-optimal care and poor health outcomes among dual eligibles with SMI. Integrated dual-eligible special needs plans (integrated D-SNPs) are a type of Medicare Advantage (MA) plan that contracts with state Medicaid agencies to cover some or all Medicaid services, coordinate Medicare and Medicaid benefits, and streamline administrative processes for dual eligibles. Without integration, Medicare and Medicaid each have a financial incentive to shift costs to the other program, affecting care delivery in ways that may not benefit patients. Integrated D-SNPs aim to address these issues by better aligning financial incentives toward “whole person” care consistent with clinical guidelines and patient preferences. This study aims to fill this gap using novel linked data capturing the entirety of Medicare and Medicaid services for 100% of dual eligibles with SMI from 2018-2027. We will use a concurrent- embedded mixed-methods design integrating a quantitative trial emulation approach with difference-in- differences (Aim 1) and survival (Aim 2) analyses with qualitative study of D-SNP implementation (Aim 3). Aims 1-2 will assess how integrated D-SNP enrollment influences care utilization and quality indicators (Aim 1) and mortality (Aim 2) among dual eligibles with SMI. Aim 3 will characterize integrated D-SNP implementation for dual eligibles with SMI with the goal of identifying promising practices and areas for improvement.

PROJECT NARRATIVE This study will evaluate how integrated Dual Eligible Special Needs Plans (D-SNPs), which integrate Medicare and Medicaid benefits for individuals dually eligible for Medicare and Medicaid, impact healthcare utilization, care quality, and mortality among people with serious mental illness.