New research about legal cannabis has revealed a sobering statistic. In states where recreational marijuana has been legalised, teenagers are suffering higher rates of addiction.
The study of 505,796 respondents was carried out by researchers from New York University's School of Medicine.
It compared use of the drug before and after legalisation in the US.
The proportion of people aged 12 to 17 who reported cannabis use disorder grew from 2.18 percent to 2.72 percent.
Chris Wilkins, a senior drug researcher at Massey University says the research is a "red flag".
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"It's an indicator, it's definitely a red flag given the negative trajectories when people use cannabis at that young age," he told The AM Show on Thursday.
He said although the data regarding young people and cannabis use was interesting, there are other aspects of the study people should pay attention to as well.
"One of the more solid findings is the actual increase in use and frequent use was in the 26-year-olds and older," he said.
"It seems to be its more the adult people who would usually transition out of cannabis are now coming back in to the market now that it's legal."
The other side of the research mentions social justice objectives. Legalisation of cannabis has potential to provide important social benefits such as equity around criminal justice.
" There's different objectives in legalisation for example reducing the black market, the gangs, becoming wealthy on cannabis, reducing arrest particularly for Maori," said Wilkins.
"Part of this debate is deciding which of those objectives you out the most value on."