Hair Testing Reveals Stronger Links Between Teen Cannabis Use and Memory Problems Than Self-Report Alone | Research

The takeaway

Combining hair toxicology with self-reported cannabis use in 13- to 14-year-olds uncovered cognitive deficits that self-report alone missed.

Researchers studying adolescent cannabis use and cognition; parents and educators interested in how teen cannabis use relates to cognitive performance.

r = -0.33 correlation between past-year cannabis use and working memory performance

What the researchers found

Cannabis-using teens scored lower on episodic memory tasks, and higher THC metabolite levels in hair correlated with poorer verbal ability, inhibitory control, working memory, and episodic memory.

Why it matters

Self-reported cannabis use in teens is notoriously unreliable. This study shows that adding hair toxicology testing reveals brain-behavior relationships that would otherwise go undetected, suggesting the true cognitive impact of early cannabis use may be underestimated in studies relying solely on self-report.

The numbers in context

Cannabis users scored lower on Picture Memory (p = .03). Within users, THCCOOH correlated negatively with Picture Vocabulary (r = -0.20, p = .03) and Flanker Inhibitory Control (r = -0.19, p = .04). Past-year use correlated negatively with List Sorting Working Memory (r = -0.33, p = .0002) and Picture Sequence Memory (r = -0.19, p = .04).

How the study worked

Cross-sectional analysis of 246 participants (123 cannabis users matched with 123 controls) from the ABCD Study Year 4 follow-up. Hair samples were analyzed by LC-MS/MS and GC-MS/MS for cannabinoid concentrations. Cognitive performance was measured using the NIH Toolbox Cognitive Battery.

What this study cannot tell us

Cross-sectional design prevents determining whether cannabis use caused the cognitive differences or whether pre-existing cognitive vulnerabilities predisposed teens to use cannabis. The matched-pair approach controls for demographics but cannot eliminate all confounders.

How to read the evidence

Moderate: well-designed cross-sectional study with objective hair toxicology measures, but cannot establish causation and has a relatively small matched sample.

When this study was published

2024 study using ABCD Study data from 2021-2022.

The bigger picture

As cannabis legalization expands and potency rises, accurate measurement of adolescent use becomes increasingly important. Hair testing could become a standard complement to self-report in neurodevelopmental research, helping clarify the cognitive stakes of early cannabis exposure.

Questions still open

Do the cognitive deficits associated with hair-confirmed cannabis use persist or worsen as these teens are followed longitudinally? Would hair toxicology reveal even stronger brain-behavior relationships in younger adolescents?

Common questions

Why does hair testing matter for cannabis research?

Teens often underreport cannabis use. Hair retains THC metabolites for weeks to months, providing a more objective measure that revealed cognitive correlations self-report missed.

Which cognitive abilities were most affected?

Working memory showed the strongest association with self-reported use (r = -0.33), while hair-detected THC metabolite levels were linked to poorer verbal ability and inhibitory control.

Read the original research

Cannabis use and neurocognitive performance at 13-14 Years-Old: Optimizing assessment with hair toxicology in the Adolescent brain cognitive development (ABCD) study.

Addictive behaviors, 150, 107930

View on PubMed ↗Publisher’s paper ↗

Citation

Wade, Natasha E; Wallace, Alexander L; Huestis, Marilyn A; Lisdahl, Krista M; Sullivan, Ryan M; Tapert, Susan F. (2024). Cannabis use and neurocognitive performance at 13-14 Years-Old: Optimizing assessment with hair toxicology in the Adolescent brain cognitive development (ABCD) study.. Addictive behaviors, 150, 107930. https://doi.org/10.1016/j.addbeh.2023.107930