Lower smoking rates are being linked with a drop in cannabis use among teenagers.
The number of young Kiwis who use cannabis is on the decline, and researchers think it's linked to lower rates of drinking and smoking tobacco.
Otago University research published Friday in the New Zealand Medical Journal has revealed a drop in teens using cannabis at least once from 38 percent in 2001 to 23 percent in 2012.
Researcher Jude Ball says there are some groups who have seen more of a decrease than others.
"The biggest declines have been among Māori students, younger students and those at lower-decile schools."
She says the results are surprising in light of increasingly liberal views on cannabis, with a referendum on recreational use to take place at next year's election.
So the researchers are adamant there will not be a spike in cannabis use among teenagers, even if the referendum passes.
"It seems to be because alcohol use and tobacco use is continuing to go down," said Ball. "It's quite likely the decline in tobacco use in young people has contributed to this decline."
The number of teens who use cannabis often halved from 6 to 3 percent over the period. Use of other psychoactive substances has also declined amongst teens, so the researchers say the drop "cannot be explained by young people using other substances instead".
The data came from the Youth 2000 surveys, conducted in 2001, 2007 and 2012. The latter is believed to be the most recent published data on cannabis use by Kiwi teenagers.
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Use of alcohol, New Zealand's most harmful drug when measured by health outcomes and costs, has been rising in recent years - with most of the increase coming from older Kiwis, with fewer teens drinking hazardously than in previous years.