Steady rate of marijuana use associated with decline in cigarette, alcohol use in adolescents

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In 8th, 10th, and 12th grades, marijuana prevalence significantly increased for youth who had never smoked and never drank alcohol.
In 8th, 10th, and 12th grades, marijuana prevalence significantly increased for youth who had never smoked and never drank alcohol.

Adolescent marijuana prevalence would be at or near record highs if cigarette use had not declined since 2005 and the perceived risk of marijuana is associated with its use, according to a study published in Pediatrics.

Richard Miech, PhD, from the Institute for Social Research at the University of Michigan, led a team of researchers in analyzing the inverse connection between marijuana prevalence and perceived risk of use. They tested two hypotheses regarding the lack of increase in marijuana prevalence since 2005. The first hypothesis points to the substantial decline in adolescent cigarette and alcohol use during the past decade that has brought their prevalence to historic lows. The second is how the perceived risk of harm now plays a smaller role in marijuana use.

Data were analyzed from the annual Monitoring the Future study, which uses self-administered questionnaires in school classrooms to survey US adolescents. Independent nationally representative samples of 8th, 10th, and 12th grade students were surveyed each year from 1991 to 2016. The cumulative sample size was 428,194 students in 8th grade, 392,195 in 10th grade, and 366,406 in 12th grade. Student response rates averaged 90%, 87%, and 83% in 8th, 10th, and 12th grades, respectively, for the combined time period of 1991 to 2016.

Since 2005, the prevalence of having ever smoked a cigarette declined by 43%, 55%, and 62% among 12th, 10th, and 8th grade students, respectively. In all 3 grades, this is now at an historic low, at 28%, 18%, and 10% in 12th, 10th, and 8th grades, respectively. Also supporting a decline in the percentage of adolescents who use cigarettes and alcohol is the growing percentage who had never used either. Since 2005, this group increased by 62% among 12th and 10th grade students, to 35% and 54%, respectively. Among 8th grade students, this group increased by 37% since 2005 and now consists of 3 of every 4 students.

In all 3 grades, marijuana prevalence significantly increased for youth who had ever smoked, youth who had never smoked and never drank alcohol, and youth who had consumed alcohol but never smoked. The projected prevalence level for marijuana use in 2016 is the highest level ever recorded during the study period (1991 to 2016) among 12th grade students. In 10th grade and 8th grade, the highest levels of projected marijuana prevalence ever recorded during the study period have occurred during the past 4 years.

The analyses also examined potential trends in perceived risk as an indicator of marijuana use. In each grade, the relative risk estimate from 2005 to 2016 varied between a small window of 0.250 and 0.299 in 12th grade, between 0.215 and 0.259 in 10th grade, and between 0.137 and 0.160 in eighth grade.

“In sum, the results support the first study hypothesis and show that expected increases in marijuana use since 2005 have been offset by a concurrent, marked decline in adolescent use of cigarettes and alcohol,” the authors concluded. “The results do not support the second study hypothesis that perceived risk of marijuana as an indicator of marijuana use has attenuated since 2005. In each grade, the association of these 2 variables did not significantly differ in 2016 as compared with 2005 and varied little in the intervening period.”

Reference

Miech R, Johnston L, O'Malley PM. Prevalence and attitudes regarding marijuana use among adolescents over the past decade. Pediatrics. 2017 Dec;140(6). doi: 10.1542/peds.2017-0982

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