Accidental overdoses cause 90 of all U.S. opioid-related deaths while suicides account for far fewer of these fatalities than previously thought, a new analysis published Tuesday suggests.br br Rising use of heroin and illicit, highly potent synthetic opioids including fentanyl has likely contributed to the unintentional death rate, which surged nine-fold between 2000 and 2017, the researchers said. Opioid suicides also went up during that time but their share of all opioid-related deaths shrank.