Changes in Prevalence of Marijuana Consumption Modes Among Colorado High School Students From 2015 to 2017

Smoking is the most prevalent mode of marijuana consumption among adolescents, but nonsmoking modes, including ingesting, vaporizing, and dabbing, have expanded in the context of legalization.^1,2 Each mode of consumption has different effects that may be associated with distinct health consequences.³ Previous research in Colorado identified smoking as the most commonly used mode of marijuana consumption among high school students and found that the prevalence of primarily ingesting marijuana declined after the implementation of retail marijuana sales.⁴ We examined changes in modes of marijuana consumption among high school students in Colorado from 2015 to 2017.

Data came from the 2015 and 2017 administrations of the Healthy Kids Colorado Survey (HKCS), a biennial cross-sectional survey conducted in Colorado public schools.⁵ The HKCS uses a 2-stage stratified cluster design with random sampling of public middle/high schools and of classrooms within schools. This study includes 9th- through 12th-grade students who reported using marijuana in the past 30 days (1664 in 2015; 3618 in 2017). The Colorado Multiple institutional review board approved the data collection. Teachers provided instructions that stated that students could choose to skip questions or not participate without consequence. All parents were given written notice of the survey 2 weeks before it was administered and could return a signed form to opt out. Approximately 5% of school districts required written parental consent for the student to participate. The secondary data analysis was deemed exempt by the Johns Hopkins Bloomberg School of Public Health institutional review board.

Two HKCS questions inquired about modes of marijuana consumption. The usual mode of consumption was assessed by asking: “During the past 30 days, how did you usually use marijuana? (select only one response).” Any use of each mode was assessed by the question: “During the past 30 days, how did you use marijuana? (select all that apply).” Response options for both questions included: smoked it, ate it, used a vaporizer, dabbed it, and used it in some other way.

Design and poststratification weights were applied to represent Colorado public high school enrollment. Weighted prevalence estimates were calculated for the usual mode and any use of each mode in 2015 and 2017. To assess the differences in the usual mode and any use of each mode across years, we used a multivariable logistic regression adjusted for race/ethnicity, sex, and grade (statistical significance, P < .05). Analyses were completed using Stata, version 14.2 (StataCorp).

Among students who reported past-month marijuana use, smoking was the most common usual mode of marijuana consumption in both years (Table 1). The prevalence of smoking as the usual mode decreased between years (adjusted prevalence ratio [aPR], 0.89; 95% CI, 0.84-0.94), whereas ingesting (aPR, 4.55; 95% CI, 2.68-7.74) and dabbing increased (aPR, 1.94; 95% CI, 1.25-3.01). More than 20% reported using a nonsmoking mode during both years (Table 2). Between 2015 and 2017, the prevalence of any smoking decreased (aPR, 0.96; 95% CI, 0.93-0.99) whereas any ingesting increased (aPR, 1.28; 95% CI, 1.11-1.48).

The modes of marijuana consumption among Colorado high school students who used marijuana in the past month shifted significantly between 2015 and 2017. The reduction in smoking marijuana could indicate that adolescents are choosing not to smoke or using nonsmoking modes because of the associated health risks of smoking, which is consistent with data showing that adolescents perceive cigarette smoking to be harmful.⁶ Adolescents may also be more likely to ingest and/or dab. These modes are important to monitor because of their unique psychoactive associations, and potential harms, including unintentional overconsumption with edibles and an increased physiological tolerance and withdrawal associated with the high tetrahydrocannabinol levels of cannabis concentrates used for dabbing.³

Despite the potential limitations associated with self-report and the inability to assess frequency of mode use and details of the “other” category, Colorado is one of few states that collects statewide data on modes of marijuana consumption among adolescents. As we continue to learn about the availability and potential harms of these products to youth, particularly with high-potency products, understanding how adolescents use marijuana is essential to developing prevention programs and campaigns to reduce risky marijuana-use behaviors.

Accepted for Publication: April 3, 2019.

Corresponding Author: Kayla N. Tormohlen, MPH, Johns Hopkins Bloomberg School of Public Health, 624 N Broadway, Room 888, Baltimore, MD 21205 (ktormoh1@jhu.edu).

Published Online: August 5, 2019. doi:10.1001/jamapediatrics.2019.2627

Author Contributions: Ms Tormohlen had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Tormohlen, Schneider.

Acquisition, analysis, or interpretation of data: Tormohlen, Johnson, Ma, Levinson, Brooks-Russell.

Drafting of the manuscript: Tormohlen.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Tormohlen, Schneider, Ma.

Obtained funding: Johnson, Brooks-Russell.

Administrative, technical, or material support: Johnson, Brooks-Russell.

Supervision: Johnson.

Conflict of Interest Disclosures: None reported.

Funding/Support: The data used for this study were collected under contracts with the Colorado Department of Public Health and Environment (Drs Levinson and Brooks-Russell, principal investigators). This work was supported by National Institute on Drug Abuse grant T32DA007292 (Mses Tormohlen and Schneider and Dr Johnson, principal investigators).

Role of Funder/Sponsor: The National Institute on Drug Abuse and Colorado Department of Public Health and Environment had no role in determining study design, data collection, analysis, or interpretation, writing the report, or the decision to submit the report for publication.

Disclaimer: The content is solely the responsibility of the authors and does not necessarily reflect the official views of the National Institutes of Health.

Meeting Presentation: These data were presented at the 2018 Scientific Meeting of the Research Society on Marijuana; July 28, 2018; Fort Collins, Colorado.