Table 1.

Search strategy

Review Question	Do mental health issues (including both symptoms of psychological distress and diagnosed psychiatric disorder) increase the risk for opioid overdose?
Search Concepts1	Mental Health: mental health, mental illness, psychiatric disorder, health care access, social service access; despair, anguish, disability, vulnerability, stigma, social isolation, social exclusion, marginalization Overdose (fatal and non-fatal): poisoning, drug-related poisoning, side-effects/adverse reactions, toxicity, death, morbidity, mortality, overdose Opioids: People who use opioids (medical/non-medical), prescription and non-prescription, oral and injection
Databases	MEDLINE (Ovid), Embase (Ovid), PsycINFO (EBSCOhost), CINAHL (EBSCOhost), Google Scholar, Cochrane Central Registry of Controlled Trials (CENTRAL), and Cochrane Drug and Alcohol Group (CDAG) Specialized Registry
Other Search Strategies	In addition to searching electronic databases, additional searches on clinicaltrials.gov, a comprehensive grey literature search (e.g., www.opengrey.eu, https://deslibris.ca), conference proceedings (e.g., Harm Reduction International, American Public Health Association), and manual searches of the references of included studies other reviews in this area, and studies that have cited the included studies were performed. The search strategy also included contacting experts and community and policy stakeholders to identify unpublished, ongoing, governmental, and other studies not otherwise retrieved through searches for this review
PECOS Criteria	Population: People who use opioids in North America, Europe, the United Kingdom, Australia, and New Zealand. Articles were only included if they had opioids (any opioid, including opioid agonist therapy) identified as a cause of overdose. Poly drug-related overdose papers were included if they included opioid overdose in the cases Exposure: Any measure of mental health as an independent variable in the article (e.g., despair, hopelessness, psychological distress, psychiatric disorder). Articles were included if they had any measure of mental health, broadly defined, as an independent variable in the article. Articles that include mental health variables as controls in their multivariable regression models, for example, were included as long as there were empirical results that showed the effects of the mental health variables on opioid overdose Comparison: Quantitative studies with comparisons between groups with different levels of mental health Outcomes: Opioid-related fatal and non-fatal overdose. Articles were included only if they had overdose as a unique/isolated outcome. Articles examining drug-related harm or mortality might include overdose but also include death or harm from other factors (e.g., motor vehicle accidents) and as such, were excluded. Articles comparing the risk of overdose between different types of opioids were excluded, as they do not address the review question of whether mental health issues increase the risk of overdose Study design: Any study design including quantitative data. Articles that contained empirical data were included. Case-reports, letters, commentaries, reviews, and editorials were excluded

¹Terms related to these key concepts were entered into all computer databases, combined using appropriate Boolean operators. All terms were searched both as subject headings as well as keywords. See Appendix A for a summary of the Medline search terms included