Elsevier

Drug and Alcohol Dependence

Volume 166, 1 September 2016, Pages 159-167
Drug and Alcohol Dependence

Full length article
Age, period, and cohort effects in synthetic cannabinoid use among US adolescents, 2011–2015

https://doi.org/10.1016/j.drugalcdep.2016.07.018Get rights and content

Highlights

  • Synthetic cannabinoid use is declining in US adolescents.

  • Declines are not uniform across demographic groups.

  • Younger cohorts who use marijuana regularly are declining at slower rates.

  • Younger cohorts with educated parents are declining in use at slower rates.

  • Risk factors for use have remained stable despite decreases in overall prevalence.

Abstract

Background

Synthetic cannabinoids use has been a public health concern given association with hospitalization and death among users. While national reports estimate that reported use is declining among adolescents, differences by birth cohort may indicate subgroups who remain at higher risk, both in the overall adolescent population and among demographic subgroups.

Methods

We estimated age, period, and cohort models of self-reported past-year synthetic cannabinoid use (queried as “synthetic marijuana” [“K2,” “Spice”]) among 54,865 adolescents aged 13–19 attending high school from 2011 to 2015.

Results

Past-year use decreased from 11.86% in 2011 to 4.75% in 2015. This decrease was best represented as a linear downward trend. When stratified by key covariates, however, results indicated evidence of a positive cohort effect for students of higher socioeconomic status (SES). For those students, use did not decrease at the same rate as the overall population; younger cohorts of high SES students remain at higher risk for synthetic cannabinoid use than older cohorts as well as lower SES peers. A similar and stronger association was found for frequent marijuana users (≥20 occasions of past-year use). Multi-level models indicated that groups at highest risk included older adolescents, Hispanics and other/mixed race students, cigarette users, and frequent marijuana users.

Conclusion

Synthetic cannabinoid use is associated with morbidity as well as mortality; continued attention to reducing synthetic cannabinoid use remains an important public health priority to maximizing student health.

Introduction

Synthetic cannabinoid use is among the newest drug-related public health threats in the United States (US). Synthetic cannabinoids are research chemicals that are intended to mimic tetrahydrocannabinol (THC)—the main psychoactive component in naturally occurring cannabis (marijuana; Zawilska and Andrzejczak, 2015). These chemicals are typically sprayed onto herbal mixtures and commonly sold under names such as “K2” and “Spice” and marketed as “legal” replacements for natural marijuana. Use of synthetic cannabinoids is linked to numerous adverse effects, including anxiety and delusions as well as tachycardia, vomiting, and as described below, seizure and poisoning among some users (Cooper, 2016). While numerous synthetic cannabinoid compounds have been banned or controlled in the US (at the federal and/or state-level) and throughout Europe, new compounds continue to emerge at a rapid pace. By 2014 in Europe alone, at least 134 compounds had been discovered (with 30 new compounds discovered in 2014; European Monitoring Centre for Drugs and Drug Addiction, 2015).

Seizures and poisonings secondary to synthetic cannabinoid use have generally increased in recent years. For example, synthetic cannabinoids were identified in 37,500 seizures in the US in 2014 while 2892 were identified in 2010 and 22,087 in 2011. There were also more reported poisonings related to synthetic cannabinoid use in 2015 (7779) than in any previous year (i.e., 6968 in 2011, 5230 in 2012, 2668 in 2013, and 3682 in 2014), with spikes in some areas such as New York City (Law et al., 2015, Palamar et al., 2016). Despite increases in seizures and poisonings in recent years, prevalence of self-reported use actually appears to have decreased, at least among youth. Monitoring the Future (MTF) is the only nationally representative survey in the US that queries use of synthetic cannabinoids, and among high school seniors in the MTF sample, in years 2011–2013, one out of ten seniors self-reported use, but self-reported use has decreased to about five percent 2015 (Johnston et al., 2015, Palamar and Acosta, 2015). Previous studies focusing on MTF samples have found demographic and other differences in reported use such as lower risk among girls compared with boys, and marijuana and other substance users are at particularly high risk for reporting use (Palamar and Acosta, 2015, Patrick et al., 2015).

An overall decrease in prevalence, however, may mask variation specific to particular subgroups of adolescents. Given that use of these compounds is often associated with deleterious outcomes (Law et al., 2015) and seizures and poisonings continue to increase, a focus on estimating the potential for cohort effects is warranted. Cohort effects occur when particular age groups evidence particular health patterns that differ from other individuals observed at the same time period (Keyes et al., 2010). The emergence of cohort effects has two central implications for etiology and intervention. First, if there are particular groups that are not experiencing the same decrease in self-reported synthetic cannabinoid prevalence compared with other groups, then the risk factors particular to those groups should be scrutinized for potential etiological relevance. For example, given that frequent marijuana use is associated with use of synthetic cannabinoids (Caviness et al., 2015, Palamar and Acosta, 2015, Winstock and Barratt, 2013), we might expect frequent marijuana users to have a slower decline in synthetic cannabinoid use compared with other adolescents. If this protracted decline is also particular to younger age groups among whom neurological development may be more fragile, adverse consequences may be heightened. Second, health patterns that are aggregated by cohort suggest that need for target efforts at prevention and treatment, as well as allocation services and planning that attend to the particular groups at highest risk for the outcomes of interest.

MTF includes an annually conducted cross-sectional survey of US high-school attending adolescents, querying use of multiple drugs including synthetic cannabinoids since 2011. As such, these data present an opportunity to estimate age, period, and cohort effects in self-reported synthetic cannabinoid use. Therefore, the present study formally decomposes variance in synthetic cannabinoid use into age, period, and cohort effects, and further, we estimate whether there is variation in age, period, and cohort effects by subgroups defined by sex, parental education (an indicator of socioeconomic status [SES]), race/ethnicity, and frequent marijuana use. Finally, we estimate multi-level models of synthetic cannabinoid use with random period and cohort effects to assess the stability of risk factors for use over time.

Section snippets

Sample

MTF has sampled 8th, 10th, and 12th grade students in ∼130 U.S. public and private high schools in the US annually since 1991. Included measurement years were 2011 through 2015, representing birth cohorts 1992–2002. High schools are selected under a multi-stage random sampling design with replacement. Schools are invited to participate for two years. Schools that decline participation are replaced with schools that are similar on geographic location, size, and urbanicity. The overall school

Results

Past year synthetic cannabinoid use increased across age, in all study years (see Fig. 1). In the figure, we removed 12- and 20-year-old students due to low sample size (12: N = 5; 20: N = 273). Concomitantly, past year use decreased among US adolescents across the study period. For example, past year use among 12th grade students decreased from 11.86% in 2011–4.75% in 2015.

Age-period-cohort modeling fitting is shown in Table 1. In the total sample, and by sex, the linear term for the overall trend

Discussion

The present results indicate that while use of synthetic cannabinoids is declining overall among US adolescents, the declines in use are not uniform across demographic groups. Specifically, young adolescents who use marijuana regularly as well as those whose parents have greater than high school education are declining in synthetic cannabinoid use at slower rates than other adolescents. Further, risk factors for use have remained stable across time despite the decreases overall in prevalence,

Conflict of interest

No conflict declared.

Role of funding source

Nothing declared.

Contributors

Dr. Katherine Keyes drafted the paper, Ms. Caroline Rutherford and Ms. Ava Hamilton performed analyses and provided critical revisions to the paper, and Dr. Joseph Palamar drafted sections of the paper. All authors have approved the final paper.

Acknowledgements

This study was supported by National Institutes of Health Grants AA021511 (Keyes) and K01DA038800 (Palamar). Monitoring the Future data collections are supported by National Institutes of Health Grant R01DA001411 (Johnston). Dr. Keyes and Ms. Rutherford had full access to all of the data in the study and jointly take responsibility for the integrity of the data and the accuracy of the data analysis.

References (33)

  • Z.D. Cooper

    Adverse effects of synthetic cannabinoids: management of acute toxicity and withdrawal

    Curr. Psychiatry Rep.

    (2016)
  • S.T. Ennett et al.

    School and neighborhood characteristics associated with school rates of alcohol, cigarette, and marijuana use

    J. Health Soc. Behav.

    (1997)
  • European Monitoring Centre for Drugs and Drug Addiction

    New psychoactive substances in Europe

    An Update from the E.U. Early Warning System(March 2015)

    (2015)
  • L.D. Harrison

    The validity of self-reported data on drug use

    J. Drug

    (1995)
  • T.R. Holford et al.

    Comparison of smoking history patterns among African American and white cohorts in the United States born 1890–1990

    Nicotine Tob. Res.

    (2016)
  • J.L. Humensky

    Are adolescents with high socioeconomic status more likely to engage in alcohol and illicit drug use in early adulthood?

    Subst. Abuse Treat. Prev. Policy

    (2010)
  • Cited by (0)

    View full text