Early cannabis initiation is associated with dual simultaneous substance use and tri-use
Authors: Goncalves Priscila Dib , Marziali Megan , Castaldelli-Maia João Mauricio , Martins Silvia 
Published: March 2022

Introduction: Cannabis use combined with other substances, such as tobacco and/or alcohol, is related to heavy patterns of substance use and adverse social outcomes. We aimed to examine whether early age of cannabis initiation was associated with dual simultaneous substance (tobacco + cannabis / alcohol + cannabis) use and tri-use (tobacco + alcohol + cannabis). Methods: We included participants aged between 12-21 years old (n= 21,127) that reported any cannabis use in the 2016-2019 National Survey on Drug Use and Health. Blunt use was defined as smoking part of a cigar with cannabis in it (“taking some tobacco out of a cigar and replace it with marijuana”) and simultaneous alcohol/cannabis use as “using marijuana/hashish at the same time or within a couple of hours of last alcohol use”. We created four-level categorical variables, one for the exposure (age of cannabis initiation) and one for the outcome (simultaneous use). The exposure variable was comprised of the following levels based on different adolescent developmental stages: 1) 12-13 years old; 2) 14-15 years old, 3) 16-18 years old), and 4) 19-21 years old. The four outcome categories were defined as: 1) cannabis use only (no simultaneous use), 2) blunt use (simultaneous cannabis and tobacco use), 3) simultaneous alcohol/cannabis, and 4) tri-use (tobacco, cannabis and alcohol). Weighted multinomial logistic regression was used to obtain adjusted odds ratios (aOR) for categories of use, adjusting for sociodemographic characteristics (reference outcome category: cannabis use only). Results: Most participants were 16+ years old (88%), non-Hispanic white (56%), with a family income equal or higher than $40K (54%) and a mean age of cannabis initiation of 15 years old. When examining simultaneous use outcomes, 70% of the participants reported some form of simultaneous use (54.85% blunt use, 14.72% tri-use, and 1.12% simultaneous alcohol/cannabis). Regarding age of cannabis initiation, 18.97% started at age 12-13, 31.85% at age 14-15, 42.18% at age 16-18 and 7.00% at age 19-21. Cannabis initiation in early adolescence (< 16 years old) was associated with simultaneous use outcomes when compared to cannabis initiation at age 16 and older. More specifically, when comparing with cannabis initiation at age 19-21, individuals reporting cannabis initiation at age 12-13 had 24.26 times the likelihood of tri-use (95% CI=17.33-33.95); and 6.64 times the likelihood of blunt use (95% CI=5.15-8.55), however, no associations were found with simultaneous alcohol/cannabis use (aOR 2.98, 95% CI= 0.94-9.37). When using cannabis initiation at age 16-18 as reference, cannabis initiation at age 12-13 was associated with six times the likelihood of tri-use (95% CI= 5.02-7.86), three times of blunt (95% CI= 2.42-3.71), and twice of simultaneous alcohol/cannabis use (95% CI= 1.26-4.40). Conclusions: Cannabis initiation in early adolescence was associated with dual and tri- simultaneous substance use. Interventions focused on delaying cannabis initiation could have a positive impact on decreasing dual and tri-substance use. Considering that 1 in 5 individuals reporting cannabis use started in early adolescence, primary prevention strategies should start before the age of 12.