U.S. teens smoke the most marijuana in the world, have the highest mortality in the world and have high binge drinking rates, a worldwide study found. A study published in The Lancet examined challenges and problems faced by 1.8 billion young people in the world -- including 40 countries overall and 27 nations described as wealthy. U.S. adolescents die a violent death -- due to guns or vehicle fatality -- as much as 20 times more than teens in any other wealthy developed nation, the New York Daily News reported. Following the United States in violent deaths were New Zealand and Portugal. Singapore, the Netherlands and Japan had the lowest rates of violent teen deaths. The study found Canada, Spain and France followed U.S. youth in smoking the most marijuana. The developed countries that led the world in binge drinking were Austria, Ireland and the United States. Among all the countries studied, the Pacific island of Tonga had the highest rate of obesity for those ages 13-15, but the United States led the wealthy nations with most obese teens, followed by Canada, Greece, Italy and Malta. Despite the high U.S. teen obesity rate, U.S. teens exercise as much, or more, than young people in any other country in the study -- especially boys.