New Zealand should steer a middle course between strict prohibition and complete legalisation when and if it overhauls cannabis laws, University of Otago researchers say.
The recent passing of the Misuse of Drugs (Medicinal Cannabis) Amendment Act by Parliament and the planned binding referendum on the potential legalisation of the drug — to be held in conjunction with the 2020 general election — meant there needed to be more debate on cannabis-related harm, University of Otago Christchurch doctors Joseph Boden and David Fergusson said.
"Cannabis has multiple harmful effects which are particularly evident for young users, and the extent to which legalisation is beneficial is by no means clear," the men wrote in the editorial in the latest New Zealand Medical Journal, published today.
"Given this context, the most prudent course of action for New Zealand to follow is to develop policies which eliminate the adverse effects of prohibition while at the same time avoiding the possible adverse consequences of full legalisation."
Dr Boden, associate professor of psychological medicine, worked with emeritus professor Fergusson — who died prior to the editorial appearing — on an analysis of data from the Dunedin Multidisciplinary Health and Development Study and the Christchurch Health and Development Study.
Both studies have questioned participants about cannabis use — more than 75% had used the drug and about 15% had developed a pattern of heavy use or dependence at some point.
The evidence showed resoundingly that cannabis use was common, but also that it was associated with educational delay, welfare dependence, and increased risk of psychotic symptoms, depression, motor vehicle accidents and respiratory impairment.
"Because cannabis is an illegal drug, the harms associated with it may have been underestimated, as use has been suppressed to some degree by its legal status," the editorial said.
However, it was also clear prohibition had consequences, such as criminalising otherwise law-abiding citizens.
"It is critical for any change in the legal status of cannabis to be undertaken with caution, and to be fully evaluated at each stage to determine the extent to which these changes are leading to increased cannabis-related harm."
Although advocating prudence, the authors did recommend the decriminalisation of possession of cannabis for over 18s, as well as supply of small amounts to adults — in step with recommendations of the Mental Health inquiry.
They also supported higher penalties for supplying cannabis to under 18s, and more money to support mental health services which specialised in cannabis-related harm.
