INTRODUCTION: Novel psychoactive substances (NPSs), due to rapid emergence and evolving use patterns, pose a significant public health surveillance challenge. Traditional surveillance lags street-level reality, necessitating the exploration of novel strategies and data sources like Reddit for continuous NPS trend monitoring and presenting a public dashboard.

METHODS: We mined data from 60,601 subreddits between January 2015 and June 2025 for seven NPSs (kratom, xylazine, medetomidine, nitazenes, tianeptine, bromazolam, and 2C-B) using keyword-variants. We performed Mann-Kendall trend tests to assess temporal patterns, computed correlations to compare post volumes with National Forensic Laboratory Information System (NFLIS) drug report counts (2015-2024), conducted cross-correlation analyses at ±2-year lags to identify lead-lag relationships, and created a public dashboard for data visualization.

RESULTS: The dataset comprised 328,223 posts from 139,901 accounts. We observed moderate to strong correlations between Reddit volumes and three out of five NPSs with NFLIS reports: bromazolam (ρ = 0.81, p < 0.001), tianeptine (ρ = 0.48, p = 0.04), xylazine (ρ = 0.60, p < 0.001). Cross-correlation analyses indicated Reddit discussions preceded NFLIS reports for medetomidine (ρ = 0.93, lag = -2 years), bromazolam (ρ = 0.86, lag = -1year), tianeptine (ρ = 0.81, lag = -2years), and xylazine (ρ = 0.62, lag = -2years), suggesting Reddit discussions as a potential leading indicator. Co-mention of other substances with NPSs often matched known trends from retrospective data.

CONCLUSION: Reddit-based surveillance provides timely and complementary signals to traditional forensic systems for NPS monitoring. Interactive visualizations and downloadable aggregated statistics are available via our dashboard.