Researchers used data from 34,514 drivers aged 16 and up who reported past-year alcohol and cannabis use. By Maureen Meehan A recent report revealed that more than 40% of U.S. drivers who use both alcohol and marijuana reported driving under the influence of one or both of the substances, according to a new study. While more than half of drivers said they did not get behind the wheel while intoxicated, 42% admitted they did. They answered questions as part of the National Survey on Drug Use and Health from 2016 to 2019. The Columbia Mailman School study was published in the American Journal of Preventive Medicine.