Examining Safer Opioid Supply Policies

This is a letter to the editor to raise concerns regarding the design and conclusions of a recent cohort study by Nguyen et al in JAMA Internal Medicine. At least one of authors involved in writing this letter were also involved in another recent population-based cohort study in a separate journal using individual-level data that reached different conclusions. They suggest that although the ecological design used by Nguyen et al can be useful, this design is prone to well-known biases regarding attribution. In this case, misclassification in exposure and outcome exacerbate these biases.