Cost of health problems caused by stock market volatility: An empirical study in Taiwan

•This study analyzes the link between financial market uncertainty and higher medical expenses using a vast Taiwanese healthcare dataset.•The study investigates the health-related costs of risky stock investments due to market volatility.•It covers all stocks in the market, providing a more representative sample than previous studies.•The research emphasizes the economic cost of health issues caused by market fluctuations, addressing a gap in literature mostly concerned with financial losses.•The research underlines the need to account for health impacts and associated costs when assessing stock market investment risks and rewards. This study highlights the often-overlooked health impacts and related costs endured by individual investors due to market volatility. Leveraging Taiwan's unique market characteristics and healthcare system, we underscore the economic repercussions of health degradation induced by market instability. Analyzing daily medical costs for depression and hypertension patients over 11 years reveals the impact of market turbulence. Specifically, a standard deviation increase in daily market volatility aligns with 4% and 12% surges in daily emergency and outpatient spending, respectively. To avert confounding biases, our empirical models account for market regimes and weather factors, and the outcomes are corroborated through robustness tests.