Marijuana use in typically developing youth was associated with altered connectivity between key brain networks (DMN-ECN) but not cognitive deficits, while alcohol use showed the opposite pattern — cognitive effects without connectivity changes.
Parents, adolescent health providers, neuroscientists, and cannabis policy researchers
What the researchers found
Marijuana use was associated with higher DMN-ECN connectivity (p=0.0066) but no neurocognitive performance changes; alcohol use showed no connectivity changes but was associated with better working memory, flexibility, attention, and executive function — likely confounded by socioeconomic factors.
Why it matters
The dissociation between brain changes and cognitive performance for marijuana is intriguing — altered connectivity without cognitive deficits could represent either compensation or a preclinical change preceding later problems.
The numbers in context
520 for connectivity analysis; 4,197 for cognitive analysis; marijuana: DMN-ECN connectivity F(2,507)=5.08, p=0.0066, q=0.039; alcohol: better working memory (p=0.020), mental flexibility (p<.0001), attention (p=0.019).
How the study worked
Cross-sectional analysis of the Philadelphia Neurodevelopmental Cohort, using regression models to examine substance use associations with triple-network resting-state connectivity (n=520) and neurocognitive performance (n=4,197).
What this study cannot tell us
Cross-sectional design; self-reported substance use; cannot determine causation; alcohol's cognitive associations may reflect socioeconomic confounding; no longitudinal follow-up.
How to read the evidence
Large sample from an established neurodevelopmental cohort with neuroimaging, but cross-sectional design and self-reported use limit causal inference.
When this study was published
Published in 2026, using data from the Philadelphia Neurodevelopmental Cohort.
The bigger picture
Finding brain connectivity changes without cognitive deficits suggests marijuana's effects on the developing brain may be subclinical initially — raising questions about whether these changes predict later problems.
Questions still open
- Do marijuana-related connectivity changes predict cognitive decline over time? Is the DMN-ECN hyperconnectivity compensatory or pathological?
Common questions
Does teen marijuana use affect the brain?
Is marijuana or alcohol worse for teen brains?
Read the original research
Associations Between Youth Marijuana and Alcohol Use, Neurocognitive Performance, and Triple-Network Resting-State Connectivity.
Biological psychiatry. Cognitive neuroscience and neuroimaging
Citation
Blyth, Sophia H; Hill, Lauren D; Huang, Anna; Woodward, Neil D; Rogers, Baxter P; Vandekar, Simon; Ward, Heather Burrell. (2026). Associations Between Youth Marijuana and Alcohol Use, Neurocognitive Performance, and Triple-Network Resting-State Connectivity.. Biological psychiatry. Cognitive neuroscience and neuroimaging. https://doi.org/10.1016/j.bpsc.2025.12.014
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