Approximately 10 million people in France use opioid medications each year, with problematic use being more frequent in France than in other European countries. Due to their euphoric and addictive effects, these medications raise concerns - particularly about their potential role in cancer development and increased mortality risk. Opioids derive from opium, which was classified as carcinogenic by the IARC-WHO in 2020, and animal studies suggest similar harmful effects from opioids. However, human studies remain limited due to insufficient data. To address this gap, this project aims to combine data from eight large international cohorts (France, United States, United Kingdom, Scotland, Australia, Iran) to rigorously investigate the long-term health effects of opioid use, particularly regarding cancer and mortality risks.
