Rosoff DB, Smith GD, Lohoff FW, et al. - Researchers used genetically based methods to determine the possible bidirectional links between genetic liability for prescription opioid and other nonopioid pain medications and both major depressive disorder (MDD) and anxiety and stress-related disorders (ASRD). They obtained the data from genome-wide association studies from participants who were of mainly European ancestry that were part of the population-based UK Biobank and Lundbeck Foundation Initiative for Integrative Psychiatric Research studies. Among 737,473 participants, increased risk of both MDD and ASRD in relation to genetic liability for increased prescription opioid use was demonstrated by single-variable mendelian randomization. In bidirectional analyses, increased prescription opioid use risk was observed in relation to genetic liability for MDD, but not ASRD. Overall, evidence for possible causal links between the genetic liability for increased prescription opioid use and the risk for MDD and ASRD was suggested by the results of this mendelian randomization analysis.