Teen Marijuana Use Alters Brain Network Connections But Not Cognitive Performance
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.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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).
Why This Research 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 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.
What This Study Doesn't Tell Us
Cross-sectional design; self-reported substance use; cannot determine causation; alcohol's cognitive associations may reflect socioeconomic confounding; no longitudinal follow-up.
Questions This Raises
- ?Do marijuana-related connectivity changes predict cognitive decline over time?
- ?Is the DMN-ECN hyperconnectivity compensatory or pathological?
Trust & Context
- Key Stat:
- Evidence Grade:
- Large sample from an established neurodevelopmental cohort with neuroimaging, but cross-sectional design and self-reported use limit causal inference.
- Study Age:
- Published in 2026, using data from the Philadelphia Neurodevelopmental Cohort.
- Original Title:
- Associations Between Youth Marijuana and Alcohol Use, Neurocognitive Performance, and Triple-Network Resting-State Connectivity.
- Published In:
- Biological psychiatry. Cognitive neuroscience and neuroimaging (2026)
- Authors:
- Blyth, Sophia H, Hill, Lauren D, Huang, Anna, Woodward, Neil D, Rogers, Baxter P, Vandekar, Simon, Ward, Heather Burrell
- Database ID:
- RTHC-08125
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does teen marijuana use affect the brain?
This study found marijuana use altered connections between brain networks involved in self-reflection and executive control, but these changes weren't associated with measurable cognitive deficits — yet.
Is marijuana or alcohol worse for teen brains?
They appear to affect different things: marijuana changed brain connectivity patterns while alcohol was associated with cognitive performance differences. Neither finding establishes causation.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-08125APA
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
MLA
Blyth, Sophia H, et al. "Associations Between Youth Marijuana and Alcohol Use, Neurocognitive Performance, and Triple-Network Resting-State Connectivity.." Biological psychiatry. Cognitive neuroscience and neuroimaging, 2026. https://doi.org/10.1016/j.bpsc.2025.12.014
RethinkTHC
RethinkTHC Research Database. "Associations Between Youth Marijuana and Alcohol Use, Neuroc..." RTHC-08125. Retrieved from https://rethinkthc.com/research/blyth-2026-associations-between-youth-marijuana
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.