The deaths where marijuana is named as a cause involve other substances like alcohol, prescription drugs or other illegal drugs. Marijuana alone has never killed anyone, you cannot overdose on it. It would take hundreds of pounds consumed in an hour. Youamp;rsquo;d pass out before reaching anything near a lethal amount. - An employee places marijuana in a container for a client at the La Brea Collective medical marijuana dispensary in Los Angeles Tuesday, Nov. 17, 2009.