North Americans and Australians are among the tops in the world for pot-smoking, according to a paper published in the British medical journal, The Lancet.

It's estimated that more than 8 percent of people ages 15-64 in North America and Australian use marijuana at least once a year,

"Australia, New Zealand and North America have traditionally been the countries which have among the highest rates (of cannabis use)," Professor Louisa Degenhardt of the University of New South Wales in Australia told the Australian Associated Press. "That has been something demonstrated repeatedly in surveys of young people and surveys of the general population."

Europe was next in terms of annual usage followed by the Middle East and Asia, while usage rates were rising across Africa still low compared to other areas of the world.

The study was conducted by the University of NSW's National Drug and Alcohol Research Center in collaboration with the University of Queensland.

It also traces a number of adverse effects to marijuana use including an increased risk of motor vehicle crashes, impaired respiratory function, cardiovascular disease, and adverse effects of regular use on adolescent psychosocial development and mental health.

The paper included an estimate from the United Nation's Office on Drugs and Crime that marijuana was used by 166 million people or 3.9 percent of the world's population between the ages of 15 to 64 years in 2006.

Click here for more on this study in the Lancet. (Subscription required)

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