Dear Editor:

Among adolescents, Canadians lead the world in past-year cannabis use (28%). (1) The prevalence is expected to rise once the federal government legalizes recreational cannabis in 2017. (2) Identified as a public health concern, cannabis use in this population can impede cognitive and emotional brain development (3) and increase the risks of mental disorder development (e.g., social anxiety, schizophrenia) (4) and road traffic injury. (5) One often-ignored factor influencing cannabis use, however, relates to the method of consumption.

Vaporizing cannabis is a growing delivery method (6) and warrants attention for two key reasons: 1) adolescents perceive vaporizing cannabis as harmless and medicinal while overlooking its negative impact on the developing brain; (7) 2) adolescents may be more inclined to use vaporizers because many of these are designed to be portable, discreet and to produce minimal odour. Vaporizers are also available across Canada for purchase without age restrictions.

For these reasons and with cannabis legalization on the horizon, it is timely and critical to monitor trends regarding vaporized cannabis. This is the first study in Canada to examine the prevalence of vaporizer use for cannabis among adolescents. Further explored are the socio-demographic correlates of these users, which can be used as user characteristics to help tailor policies and interventions surrounding cannabis use prevention and reduction within this at-risk population.

METHODS

This study used data from the Ontario Student Drug Use and Health Survey (OSDUHS; 60% response rate), which is the longest ongoing population-representative health survey in Canada of adolescents' overall health and health risk behaviours (e.g., alcohol, tobacco) and is led by the Centre for Addiction and Mental Health in Toronto. Further details of this representative survey can be found elsewhere. (8)

In 2015, data on vaporizer use for cannabis were collected for the first time. Students in grades 9-12 (ages 15-18) were asked if they used e-cigarettes in the previous 12 months for marijuana, hash oil, liquid, or wax. This study presents vaporizer use data from a random half sample (split form) of 3,171 high school students, in addition to data on socio-demographic correlates, including sex, age, race, immigrant, and socio-economic status.

Analyses were based on a complex sample design with 21 strata (region by school level) and 220 primary sampling units (schools). Selection weights were applied to account for varying sampling probabilities and restore the sample to the corresponding population distribution. Descriptive, univariate, and multivariate analyses were conducted using STATA 14.

RESULTS AND DISCUSSION

The prevalence of high school students vaporizing cannabis through e-cigarettes in the previous year was 8% (n = 257; Table 1). This is a higher rate compared to the only other study examining adolescent vaporizer use internationally (5.4% among 3,245 Connecticut, US adolescents). (9) However, the current study still likely underestimates usage levels since the measure was specific to e-cigarettes. Though e-cigarettes are common devices, the range of vaporizers on the market is widening (e.g., portable, non-portable). Hence, to better monitor the prevalence of vaporized cannabis use in adolescents, future assessments should account for all vaporizer designs.

In terms of demographics, the significant multivariate correlates of having used e-cigarettes to vaporize cannabis in the previous year were: age (older, OR = 1.36), gender (male, OR = 2.21), immigrant status (Canadian-born, OR = 3.15), and father's education (high school, OR = 1.57). Practitioners and policy- makers working to curb cannabis use in Canada can use this knowledge to tailor reduction/prevention strategies that are age-, gender-, culture- and socio-economic-status-specific.

The study's cross-sectional design and self-reported data are study limitations since causal inferences cannot be made. Study strengths include a large representative, population-based sample of Ontario students and novel findings on vaporizer use in the context of a rapidly evolving legislative landscape regarding cannabis control. This study can set the stage to monitor future use of vaporized cannabis while user characteristics can inform the development of practice guidelines and policies to limit this trend in adolescents.

George Mammen, PhD, Jurgen Rehm, PhD, Sergio Rueda, PhD

Centre for Addiction and Mental Health, Institute for Mental Health Policy

Research, Toronto, ON

doi: 10.17269/CJPH.107.5747

REFERENCES

(1.) UNICEF Office of Research. Child Well-Being in Rich Countries: A Comparative Overview (Innocenti Report Card 11). Florence, Italy: UNICEF Office of Research, 2013.

(2.) Hopfer C. Implications of marijuana legalization for adolescent substance use. Subst Abuse 2014;35(4):331-35. doi: 10.1080/08897077. 2014.943386.

(3.) Volkow ND, Swanson JM, Evins AE, DeLisi LE, Meier MH, Gonzalez R, et al. Effects of cannabis use on human behavior, including cognition, motivation, and psychosis: A review. JAMA Psychiatry 2016;73(3):292-97. PMID: 26842658. doi: 10.1001/jamapsychiatry.2015.3278.

(4.) Paruk S, Burns JK. Cannabis and mental illness in adolescents: A review. S Afr Fam Pract 2015;11:1-4.

(5.) Imtiaz S, Shield KD, Roerecke M, Cheng J, Popova S, Kurdyak P, et al. The burden of disease attributable to cannabis use in Canada in 2012. Addiction 2016;111(4):653-62. PMID: 26598973. doi: 10.1111/add.13237.

(6.) Budney AJ, Sargent JD, Lee DC. Vaping cannabis (marijuana): Parallel concerns to e-cigs? Addiction 2015;110(11):1699-704. PMID: 26264448. doi: 10.1111/add.v110.11.

(7.) Roditis ML, Halpern-Felsher B. Adolescents' perceptions of risks and benefits of conventional cigarettes, e-cigarettes, and marijuana: A qualitative analysis. J Adolesc Health 2015;57(2):179-85. PMID: 26115908. doi: 10.1016/j. jadohealth.2015.04.002.

(8.) Boak A, Hamilton HA, Adlaf EM, Mann RE. Drug Use Among Ontario Students, 1977-2015: Detailed OSDUHS Findings (CAMH Research Document Series No. 41). Toronto, ON: Centre for Addiction and Mental Health, 2013.

(9.) Morean ME, Kong G, Camenga DR, Cavallo DA, Krishnan-Sarin S. High school students' use of electronic cigarettes to vaporize cannabis. Pediatrics 2015;136(4):611-16. PMID: 26347431. doi: 10.1542/peds.2015-1727.

Table 1. Prevalence and socio-demographic correlates of vaporizing
cannabis through e-cigarettes among Ontario high school students: Data
from the 2015 Ontario Student Drug Use and Health Survey

                                                  Yes vaporize
                                                 (8.2%;n = 257)
Age [M = 15.97, SD = 1.30]                    M = 16.30, SD = 1.11
Gender
   Female [47.9%]                                     6.0%
   Male [52.1%]                                       9.6%
Background
   Non-white [34.1%]                                  6.3%
   White [65.9%]                                      8.3%
Parent origins
   Both parents born in Canada [48.9%]                8.7%
   One parent born in Canada [14.3%]                  7.4%
   Neither parent born in Canada [36.8%]              6.3%
Immigrant status
   Canadian born [80.9%]                              4.2%
   Immigrant [19.1%]                                  8.3%
Mother's education
   No high school [35.8%]                            11.3%
   High school [19.0%]                                9.8%
   College/university [45.2%]                         6.0%
Father's education
   No high school [31.4%]                             8.4%
   High school [26.3%]                               11.1%
   College/university [42.3%]                         5.0%
SES (score 1-10) [M = 6.95, SD = 1.54]        M = 6.87, SD = 0.11

                                                  No vaporize
                                                (91.8%;n = 2889)
Age [M = 15.97, SD = 1.30]                    M = 15.66, SD = 1.27
Gender
   Female [47.9%]                                    94.0%
   Male [52.1%]                                      90.4%
Background
   Non-white [34.1%]                                 93.7%
   White [65.9%]                                     91.7%
Parent origins
   Both parents born in Canada [48.9%]               91.3%
   One parent born in Canada [14.3%]                 92.6%
   Neither parent born in Canada [36.8%]             93.7%
Immigrant status
   Canadian born [80.9%]                             95.8%
   Immigrant [19.1%]                                 91.7%
Mother's education
   No high school [35.8%]                            88.7%
   High school [19.0%]                               90.2%
   College/university [45.2%]                        94.0%
Father's education
   No high school [31.4%]                            91.6%
   High school [26.3%]                               88.9%
   College/university [42.3%]                        95.0%
SES (score 1-10) [M = 6.95, SD = 1.54]        M = 7.00, SD = 0.03

                                                 Unadjusted OR
                                                    (95% CI)
Age [M = 15.97, SD = 1.30]                     1.38 * (1.20-1.58)
Gender
   Female [47.9%]                                  Reference
   Male [52.1%]                                1.94 * (1.34-2.80)
Background
   Non-white [34.1%]                               Reference
   White [65.9%]                                1.16 (0.78-1.74)
Parent origins
   Both parents born in Canada [48.9%]          1.36 (0.90-2.06)
   One parent born in Canada [14.3%]           1.31 (0.71 -2.42)
   Neither parent born in Canada [36.8%]
Immigrant status
   Canadian born [80.9%]                           Reference
   Immigrant [19.1%]                           2.77 * (1.58-4.84)
Mother's education
   No high school [35.8%]                          Reference
   High school [19.0%]                          0.73 (0.43-1.22)
   College/university [45.2%]                  0.51 * (0.33-0.80)
Father's education
   No high school [31.4%]                          Reference
   High school [26.3%]                          1.55 (0.95-2.52)
   College/university [42.3%]                   0.71 (0.43-1.18)
SES (score 1-10) [M = 6.95, SD = 1.54]          0.97 (0.86-1.10)

                                                  Adjusted OR
                                               (95% CI), n = 2495
Age [M = 15.97, SD = 1.30]                     1.36 * (1.16-1.58)
Gender
   Female [47.9%]                              2.21 * (1.46-3.35)
   Male [52.1%]
Background
   Non-white [34.1%]
   White [65.9%]
Parent origins
   Both parents born in Canada [48.9%]
   One parent born in Canada [14.3%]
   Neither parent born in Canada [36.8%]
Immigrant status
   Canadian born [80.9%]                       3.03 * (1.50-6.14)
   Immigrant [19.1%]
Mother's education
   No high school [35.8%]
   High school [19.0%]
   College/university [45.2%]
Father's education
   No high school [31.4%]                      1.57 * (1.01-2.46)
   High school [26.3%]
   College/university [42.3%]
SES (score 1-10) [M = 6.95, SD = 1.54]

* p < 0.05.