A University of Queensland researcher is a major contributor to a new World Health Organisation (WHO) report on the adverse health effects of nonmedical cannabis use.
Professor Wayne Hall of the Centre for Youth Substance Abuse Research has helped identify important gaps in knowledge about a substance used by an estimated 181.8 million people globally.
"There is far less known about the long-term effects of nonmedical cannabis than about the use of alcohol and tobacco," Professor Hall said.
"There is increasing demand for treatment for cannabis-use disorders and associated health conditions in high- and middle-income countries.
"There has also been increased international dialogue on changing international policies towards cannabis – such as the legalisation of medical and recreational cannabis use in the USA – and their potential future public health impacts."
The report, by Professor Hall and Maria Renstrom and Dr Vladimir Poznyak from WHO, was published on March 4, 2016.
The report concludes with a section detailing six priority areas for future research: substance content and prevalence, neurobiology of cannabis use, health consequences, social costs, prevention, and treatment.
"For instance, we need to know more about the effects of long-term cannabis use on various cancer risks," Professor Hall said.
"We also need to know more about the effects of heavy cannabis use on coronary heart events, and the effects of cannabis use in pregnancy.
"What are the effects of acute and regular cannabis use on suicide ideation, suicide attempts and deaths from suicide?
"For a substance that is so prevalent, there are many things we still don't know about its effects that could help inform potential and current users."
The report also queries how much Tetrahydrocannabinol (THC), the molecule present in cannabis, content varies from country to country and whether increased THC content relates to an increased strain on health services.
Of the facts known about cannabis use, the report says that one in 10 people who use cannabis becomes dependent, with that figure jumping to one in three for daily users.
It also notes that cannabis is associated with the onset of schizophrenia at a younger age, plus negative outcomes such as early school-leaving, cognitive impairment, increased risk of depression and increased risk of using other illicit drugs.
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