Cannabis Use Blunts Neurocognitive Development in Adolescents

The Maturing Brain and the Cannabinoid Challenge

Adolescence represents a critical window of neurocognitive maturation characterized by rapid development in executive function, memory, and inhibitory control. While cannabis remains the most widely used illicit substance among youth in the United States, the long-term impact of early exposure on these developmental trajectories remains a subject of intense clinical debate [1, 2]. Current evidence suggests that adolescent-onset users may face more persistent deficits and less complete recovery following cessation compared to those who begin use in adulthood [3, 4]. Previous research has indicated that while short-term abstinence may improve certain aspects of executive function, other cognitive domains may show more enduring impairment [4]. Furthermore, existing longitudinal data suggests that cannabis initiation during these formative years is associated with altered neurocognitive growth across multiple functional domains [5, 6]. A new study now offers fresh insights into these developmental trajectories by combining longitudinal self-reporting with objective toxicological measures.

Rigorous Tracking via Multi-Modal Toxicology

The researchers utilized the longitudinal Adolescent Brain Cognitive Development (ABCD) Study dataset, which provided a robust sample of 11,036 participants followed from ages 9 to 17 years. This cohort, consisting of 47% female and 53% male individuals, allowed for a high-powered analysis of neurocognitive development during a period of significant brain maturation. To address the common clinical challenge of patient underreporting, the study combined self-reported substance use with objective toxicological tests, including hair, urine, breath, and oral fluid samples. Incorporating these toxicological measures improved the accuracy of identifying cannabis use within the study population, providing a more reliable foundation for assessing exposure than self-reporting alone. To isolate the specific impact of cannabis, the researchers employed longitudinal mixed methods (a statistical framework that tracks individual changes over time while accounting for both fixed and random effects) to investigate how time-varying cannabis onset influenced neurocognitive performance. The analysis was highly controlled, utilizing primary model covariates that included sociodemographics, family history of substance use disorder, prenatal substance exposure, early psychopathology, and the use of other substances. To account for potential environmental and genetic clustering, the researchers applied statistical nesting (a technique that groups data points to account for shared influences, such as being raised in the same household) for participant ID, study site, and family ID. All primary models utilized false discovery rate corrections (a method to control for false positives when performing multiple statistical tests) with a significance threshold of FDR-p < .05.

Flattened Trajectories Across Cognitive Domains

The longitudinal analysis revealed that cannabis group membership interacted with age to produce altered neurocognitive trajectories (the developmental path of mental growth and skill acquisition) across a wide array of cognitive functions. While non-using adolescents typically show steady gains in cognitive efficiency, those who initiated cannabis use demonstrated reduced improvement or flattened neurocognitive trajectories over time. This blunting of expected developmental progress was particularly evident in immediate recall and delayed memory, as well as in processing speed, inhibitory control, and visuospatial processing, with effect sizes ranging from β = -0.11 to -0.52. Furthermore, the language and working memory domains also showed significantly altered trajectories associated with cannabis use, maintaining the same range of negative beta coefficients (βs = -0.11 to -0.52). Intriguingly, the data suggest that youth who eventually use cannabis may actually show pre-existing better cognitive performance during late childhood, prior to the onset of substance use. This baseline advantage, however, appears to be offset by the subsequent lack of typical developmental growth. These findings remained significant even after the researchers accounted for within-person change (the statistical tracking of how an individual's own performance fluctuates over time) and numerous known confounding variables, such as family history of substance use and early psychopathology. For the practicing clinician, these results suggest that cannabis use during the adolescent years may effectively stall the maturation of executive functions and memory systems, regardless of a patient's initial cognitive standing, raising the prospect that future diagnostic tools could match patients to targeted interventions based on their neurobiological profile.

THC Exposure and Episodic Memory Deficits

To isolate the specific effects of different cannabinoids on the developing brain, the researchers conducted a secondary analysis focused on a sub-cohort of participants who underwent repeat toxicological hair testing (n = 645). This group, assessed between the ages of 12 and 16, consisted of 38% female and 62% male participants. By utilizing hair samples, the study could objectively distinguish between exposure to delta-9-tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, and cannabidiol (CBD), a non-intoxicating cannabinoid. These secondary models were held to a rigorous significance threshold of p < .01 to ensure the robustness of the findings within this smaller sample size. The results of this toxicological analysis revealed that hair-identified THC exposure interacting with age predicted significantly worse episodic memory (the ability to recall specific personal experiences or events) compared to the control group (β = -0.60, p = .007). In contrast, the researchers found no significant difference in neurocognitive trajectories between CBD-exposed participants and controls, suggesting that the developmental blunting observed in the larger study is specifically driven by THC. For clinicians, these data provide a clear physiological link between THC consumption and the impairment of memory systems during mid-adolescence. This distinction is critical when counseling families about the risks of high-THC cannabis products, as the findings indicate that THC exposure, rather than cannabis use in general, is the primary driver of these specific cognitive deficits.

References

1. Figueiredo P, Tolomeo S, Steele JD, Baldacchino A. NEUROCOGNITIVE CONSEQUENCES OF CHRONIC CANNABIS USE: A SYSTEMATIC REVIEW AND META-ANALYSIS.. Neuroscience and Biobehavioral Reviews. 2019. doi:10.1016/j.neubiorev.2019.10.014

2. Schreiner AM, Dunn ME. Residual effects of cannabis use on neurocognitive performance after prolonged abstinence: A meta-analysis.. Experimental and Clinical Psychopharmacology. 2012. doi:10.1037/a0029117

3. Ricci V, Fraccalini T, Martinotti G, Maina G. Cannabis cessation and neurocognitive recovery: Patterns, predictors, and clinical implications-a systematic review.. American Journal on Addictions. 2026. doi:10.1111/ajad.70156

4. Schuster R, Costello MA, Potter K, et al. Neurocognitive outcomes in adolescents with and without four weeks of cannabis abstinence: a randomized clinical trial using contingency management. Frontiers in Psychiatry. 2025. doi:10.3389/fpsyt.2025.1723633

5. Wade NE, Sullivan RM, Wallace AL, et al. Longitudinal Neurocognitive Trajectories in a Large Cohort of Youth Who Use Cannabis: Combining Self-Report and Toxicology.. bioRxiv : the preprint server for biology. 2026. doi:10.64898/2025.12.20.695698

6. Wade NE, Sullivan RM, Wallace AL, et al. Longitudinal neurocognitive trajectories in a large cohort of youth who use cannabis: combining self-report and toxicology.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology. 2026. doi:10.1038/s41386-026-02395-1