Abstract
Power outages are becoming more frequent in the United States, yet their mental health consequences remain under-identified in clinical data. Maryland is a particularly relevant setting given its mental health service utilization rate of 42.2 per 1,000 population-nearly twice the national average-and its aging grid infrastructure under increasing climate stress. We combine high-frequency power outage records (15-minute intervals) with administrative inpatient claims from the Maryland Healthcare Cost and Utilization Project State Inpatient Database to estimate how outages affect mental-health-related hospitalizations from 2018 to 2023. In the baseline, we define severe outage exposure as the count of episodes exceeding the 75(th) percentile of outage intensity and lasting at least one hour. Higher outage exposure is consistently associated with increased mental health hospitalization rates (IRR (Incidence Rate Ratio) ≈ 1.017, approximately a 1.7% increase). This association is robust to alternative severeity cutoffs (50(th) and 90(th) percentile), with effects concentrated in moderate-duration disruptions (1-3 hours) rather than prolonged outages. Instrumental-variable models using three grid infrastructure measures-transformer density, substation density, and transmission line density-indicate larger causal effects (IRR ≈ 1.35-1.52) than conventional fixed-effects models. Heterogeneity shows that effects are concentrated in large metropolitan areas and lower-poverty areas. Because hospitalization-based measures reflect both underlying need and access to care, these estimates likely understate the true population burden, particularly in underserved communities. These findings position grid reliability as a public health concern and highlight the importance of reducing recurrent short-duration outages, strengthening continuity of mental health care and medication access, and integrating health considerations into reliability planning for outage-prone communities.