Grant: Project Grant

Non-fatal opioid overdose occurs far more often than fatal overdose and represents a major and growing cause of injury among people living with mental illness, substance use problems, and unstable housing. Many opioid overdoses happen in the community, outside hospitals, and are never captured in medical records. At the same time, the unregulated drug supply has become increasingly dangerous, with fentanyl and related synthetic opioids greatly increasing the frequency, unpredictability, and severity of overdose. Despite this, most research has focused on long-term risk factors or overdose deaths, leaving critical gaps in understanding when and how overdose risk rises in the short term and whether non-fatal overdose can lead to lasting effects on the brain and thinking. This study follows approximately 300 adults living in the community who are assessed regularly over time. By using monthly check-ins, the study will identify short-term changes in mental health that occur before non-fatal opioid overdose, such as worsening symptoms of psychosis or depression. These changes are measured using tools already used in routine care, making the findings directly relevant to clinicians, outreach teams, and community providers working to prevent overdose. The study will also examine whether surviving a non-fatal opioid overdose is associated with changes in brain structure and thinking. Brain scans, cognitive testing, and blood markers of brain injury will be completed before overdose events and again at approximately six weeks after overdose, and compared with similar participants who did not overdose during the same period. Together, the results will support more targeted overdose prevention efforts, including timely naloxone distribution during high-risk periods, improved follow-up after overdose, and better identification of individuals who may benefit from enhanced monitoring and support.