A new Lancet paper co-authored by a UQ researcher states that Australians are the highest cannabis users in the world, only matched by USA and New Zealand.
The paper was published at the weekend by Professor Wayne Hall of UQ's School of Population Health and Professor Louisa Degenhardt of the National Drug and Alcohol Research Centre at UNSW.
The researchers identify that 1 in 25 people in the 15-64 age group are using cannabis, despite adverse health effects including chronic use and dependence. The paper reviews the health issues surrounding cannabis use from a public health perspective.
The most adverse effects [of cannabis] include a dependence syndrome, 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 outlines.
Regular cannabis use, especially daily, is linked to chronic health effects including bronchitis, impaired cognitive functioning, a doubled risk of schizophrenia compared to non-users, and cannabis dependence which affects one in ten users.
Professor Hall believes that the young uptake of cannabis is a likely cause for lifetime adverse health issues.
"Generally, the more people who use any drug, the earlier they start using and the more often they use, the more likely they are to experience these harms," he said.
"Evidence has strengthened for young people at risk of adverse cannabis effects. When they initiate early and become regular users in their mid-teens, they are at higher risk of psychoses and poorer psychosocial outcomes in adolescence.
"The existence of a cannabis dependence syndrome is confirmed, which means policy makers should focus on providing advice for young adults and teenagers before they commence using cannabis."
Despite the number of adverse effects, the paper states that the public health burden of cannabis is "modest", causing 0.2 percent of disease burden in Australia who have one of the highest reported rates of cannabis use.
This was 10 percent of the burden attributable to all illicit drugs.
Professor Hall urges further research on the longer term health risks of cannabis, given that cannabis use is common in developed countries.
"Information on patterns of its use should be routinely collected in epidemiological research and clinical studies so that its health effects can be better understood," he said.
Read the full publication here.
Professor Wayne Hall
October 20, 2009
The University of Queensland Australia