High-sensitivity urine testing detected THC in 25% of urban adolescents, far more than standard immunoassay screens, and cigarette smokers had 13 times the odds of also using marijuana.
Pediatricians, adolescent medicine specialists, and public health researchers studying teen substance use.
13x odds if smoking tobacco
What the researchers found
The standard immunoassay substantially underestimated THC exposure compared to high-sensitivity chromatographic testing. THC was detected in 25% of 686 adolescents. Prevalence increased with age and was higher among non-Hispanic Black participants. Active tobacco smokers had 80% prevalence of THC use (OR 13.2). Urine cotinine and THC metabolite levels were significantly correlated (r=0.60).
Why it matters
If standard drug tests underestimate adolescent marijuana use, prevalence data and clinical screening may be systematically inaccurate. The strong tobacco-marijuana concordance suggests screening for one substance should trigger screening for the other.
The numbers in context
686 adolescents. THC detected in 25%. Cigarette smokers: 80% THC prevalence, OR 13.2 for predicting THC use. Cotinine-THC correlation: r=0.60. Standard immunoassay had high specificity but only moderate sensitivity.
How the study worked
Cross-sectional study of 686 adolescents aged 12-21 seen at Zuckerberg San Francisco General Hospital (2012-2014). Urine tested using both standard immunoassay and high-sensitivity liquid chromatographic assays for nicotine and THC metabolites.
What this study cannot tell us
Single urban hospital setting may not represent all adolescent populations. Cross-sectional design cannot determine directionality of the tobacco-marijuana relationship. Urine testing captures recent use but not patterns over time.
How to read the evidence
Rated moderate because this is a reasonably large study with quantitative biomarker data, though from a single hospital setting.
When this study was published
Published in 2019 using 2012-2014 data. Vaping has since changed the dual-use landscape significantly.
The bigger picture
The quantitative correlation between tobacco and marijuana exposure levels suggests these are not just co-occurring habits but may be dose-related. As dual use becomes more common with vaping products, understanding this relationship becomes increasingly important.
Questions still open
- How much adolescent marijuana use is missed by standard screening? Does reducing tobacco use reduce marijuana use? Would high-sensitivity testing change clinical decision-making in adolescent care?
Common questions
How common is marijuana use among teens?
Why are tobacco and marijuana use so linked in teens?
Read the original research
Quantitative biochemical screening for marijuana use and concordance with tobacco use in urban adolescents.
Drug and alcohol dependence, 205, 107583
Citation
Benowitz, Neal; Nardone, Natalie; St Helen, Gideon; Addo, Newton; Jacob, Peyton; Liakoni, Evangelia; Jain, Shonul; Hooshfar, Shirin; Lynch, Kara. (2019). Quantitative biochemical screening for marijuana use and concordance with tobacco use in urban adolescents.. Drug and alcohol dependence, 205, 107583. https://doi.org/10.1016/j.drugalcdep.2019.107583
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