Understanding the impact of natural disasters on post-traumatic stress disorder and depression symptoms: An examination of counterfactual displacement scenarios.

Displacement following extreme weather events is a growing concern, yet evidence on its mental health impacts remains limited. In August 2017, Hurricane Harvey caused extensive flooding and damage in Houston, Texas, leading to substantial displacement. In this study, we take a counterfactual approach to examine how displacement scenarios affect post-traumatic stress disorder (PTSD) and depression symptoms among impacted residents. We conducted a cross-sectional survey of adult Houston residents who experienced Hurricane Harvey. Using Augmented Inverse Probability Weighting and Inverse Probability Weighted Regression Adjustment within a causal inference framework, we estimated the association between displacement and PTSD and depression symptom scores among residents affected by Hurricane Harvey. First, we estimated the Potential Outcome Means (POmeans) under counterfactual scenarios of displacement and non-displacement. We then computed the Average Treatment Effect (ATE) and the Average Treatment Effect on the Treated (ATT) for both PTSD and depression. Covariates included demographic factors, socioeconomic status, and self-reported physical health. POmeans indicated that displaced individuals had elevated PTSD and depression symptom levels compared with a counterfactual scenario in which they were not displaced. Displacement was associated with higher PTSD symptom scores (ATE: 5.88 points [95% CI, 3.37-8.39]; ATT: 5.43 [95% CI, 2.65-8.20]) and higher depression symptom scores (ATE: 1.93 [95% CI, 0.99-2.87]; ATT: 2.12 [95% CI, 1.04-3.20]). Using causal inference methods, our analysis suggests that displacement is associated with worsened PTSD and depression symptomatology. While our doubly robust approach strengthens inference, these estimates should be interpreted as associations given the potential for residual confounding from unmeasured variables. As climate-related disasters intensify, these results highlight the importance of proactive policies and mental health interventions that specifically address the psychological toll of displacement. Future studies using longitudinal designs could further elucidate the causal pathways linking disaster-related displacement to long-term mental health outcomes.