New Zealanders are among the heaviest users of cannabis in the world, an international report in the British medical journal The Lancet says.
The report, by the University of New South Wales National Drug and Alcohol Research Centre in collaboration with the University of Queensland, reviews global research into marijuana consumption.
Professor Louisa Degenhardt of the University of NSW said surveys have repeatedly shown New Zealand, Australia and North America have among the highest rates of cannabis use.
Europe was next in terms of annual usage followed by the Middle East and Asia, while usage rates were rising across Africa but from a low base in some countries.
The paper includes a UN Office on Drugs and Crime estimate that cannabis was used by 166 million people, or 3.9% of the global population aged 15 to 64 years, during 2006.
It does not give a figure for New Zealand, except to say it exceeds 8%.
The paper states one in 10 users have "cannabis dependence syndrome" placing them at risk of chronic bronchitis, psychotic symptoms especially in those with a family history of mental disorders, and also poorer education outcomes in affected youth.
Other possibly linked health effects include respiratory cancer, depression, suicide or behavioural disorders in children whose mothers used cannabis while pregnant.
A person's heart attack risk increases almost five times during the hour after they used cannabis, another study shows.
Figures supplied by drug experts at Massey University say 18% of the population have used cannabis at least once in the past year and 44% have used it at least once in their lifetime.