Early-onset smoking and vaping of cannabis: Prevalence, correlates and trends in New Zealand 14-15-year-olds

Introduction: Initiating cannabis use at an early age elevates risk of harm. Cannabis vaping is an emerging issue, and it is unknown whether the patterning and correlates of early-onset cannabis vaping differ from those of cannabis smoking.Methods: We used repeat cross-sectional data from a nationally representative biennial survey (2012-2018) of students aged 14-15 years in New Zealand (N = 11,405), response rate 65% (2012), 64% (2014-2016) and 59% (2018).Results: Between 2012 and 2018 lifetime cannabis use decreased, but regular use (past month, weekly, daily) was stable. Prevalence of past month, weekly and daily use in 2016-2018 (pooled) was 8.6%, 3.4% and 1.5%, respectively. Cannabis vaping was reported by 24% of past month cannabis users. The demographic profile of early-onset cannabis smokers and vapers was similar, with elevated use of both modes among Maori (Indigenous), same- or both-sex attracted students and those in low decile (high-deprivation) schools. Correlates were similar for both modes. Cannabis use was strongly associated with tobacco and alcohol use. The next strongest associations (after adjustment) were exposure to second-hand smoke at home, student income >$50/week and low parental monitoring of whereabouts. Past week social media use, psychological distress and low parental monitoring of spending were also associated with both modes.Discussion and conclusions: Early-onset cannabis use is much higher in structurally disadvantaged groups, and among those who use tobacco and alcohol. Comprehensive multisubstance approaches to prevention are indicated in this age group. Efforts to reduce socio-economic inequity and exposure to other risk factors may reduce cannabis-related harm.