Association between flooding and opioid overdose deaths in Appalachia

Flooding is increasingly recognized as a major public health threat, yet its potential relationship with opioid overdose mortality has received little quantitative investigation. This study examined whether severe flooding was associated with subsequent changes in opioid overdose deaths across counties in the Appalachian region of the United States, where overdose mortality has been disproportionately high. Counties experiencing severe flooding in 2011 were compared with non-flooded counties using a matched pre-post change analysis. Multiple propensity-score matching strategies (1:1, 1:2, 1:3, caliper, and full matching) were evaluated to improve comparability between groups, and multivariable linear regression models with robust standard errors estimated changes in average annual opioid overdose deaths between the three years before (2008–2010) and after (2012–2014) the flooding event. Across all matching approaches, estimated flooding effects remained positive, although statistical significance after full adjustment was retained only under the full-matching specification, which estimated approximately 1.75 additional overdose deaths per county over the post-flood period. Subgroup analyses suggested that the association was strongest among males, White populations, and adults aged 25–64 years. Because this observational study measured only the association between flooding and overdose mortality, the proposed mechanisms linking disaster-related disruption to increased overdose risk remain hypothetical and were not directly tested. These findings provide preliminary evidence that severe flooding may contribute to worsening opioid overdose outcomes in vulnerable communities and support incorporating substance-use considerations into disaster preparedness, response, and recovery planning.