The relationship between cannabis and nicotine use: A systematic review and meta‐analysis

Abstract

AbstractBackground and aimsCannabis and nicotine (tobacco or e‐cigarettes) use commonly co‐occurs and understanding their relationship can help to inform public health strategies to prevent their harms. We conducted a systematic review and meta‐analysis to estimate the association of cannabis use given prior nicotine use and vice versa.MethodsPubMed, Embase, PsycINFO, Google Scholar and a hand‐search were conducted in 2023 for longitudinal studies of the general population with no restrictions in settings (locations). Random‐effects meta‐analysis was conducted to estimate odds ratios between cannabis and nicotine use in both directions. The impact of unmeasured confounding was assessed using E‐values.ResultsFrom 5387 identified records, we included 20 studies. Among cannabis‐naïve youths, baseline use of any nicotine products was positively associated with initiation of any cannabis use at follow‐up [odds ratio (OR) = 5.39, 95% confidence interval (CI) = 3.19, 9.11; adjusted OR (aOR) = 2.59, 95% CI = 2.01, 3.32]. In nicotine‐naïve participants (youths + adults), baseline cannabis use was positively associated with the initiation of any nicotine use at follow‐up (OR = 4.08, 95% CI = 2.05, 8.11; aOR = 2.94, 95% CI =1.54, 5.61). There were no significant associations between baseline cannabis use and subsequent initiation of any nicotine (aOR = 3.29, 95% CI = 0.85, 12.76) or daily nicotine use (aOR = 2.63, 95% CI = 0.41, 16.95) among youths. The median E‐values were 5.5 for nicotine exposure and cannabis use initiation and 4.1 for cannabis exposure and nicotine use initiation, indicating that substantial unmeasured confounding would need to have a strong association with both outcomes to fully explain away the cannabis and nicotine relationship.ConclusionAlthough the evidence for associations between cannabis use and tobacco use is mixed, a majority of studies to date have found that cannabis use is associated with prior nicotine use and vice versa.