Prevalence rates of opioid use disorder (OUD) have increased dramatically, accompanied by a surge of overdose deaths—nearly 50,000 in the U.S. in 2019. While opioid dependence has been extensively studied in preclinical models, an understanding of the biological alterations that occur in the brains of people who chronically use opioids and who are diagnosed with OUD remains limited.To address this issue, researchers from Boston University School of Medicine (BUSM) have conducted the largest transcriptomic (the study of all the RNA molecules within a cell) study to date using postmortem brains from people with OUD.