What topics does this cannabis study cover?

This study covers research on: Mental Health, Neuroprotection.

Where was this research published?

Published in Psychopharmacology on May 11, 2026.

Cannabis use linked to IQ decline and executive function changes over time

Q: What did this Review find?

This comprehensive narrative review examined **21 longitudinal studies involving approximately 27,734 participants** to understand how cognitive abilities change over time with recreational cannabis use. The research included young people aged 5 to 42 years, with over 11,700 cannabis users and nearl

How does cognition change over time in young people who use cannabis recreationally? A narrative review of the longitudinal literature to date.

Psychopharmacology • May 11, 2026 • Review • Moderately Relevant

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AI Summary

This comprehensive narrative review examined 21 longitudinal studies involving approximately 27,734 participants to understand how cognitive abilities change over time with recreational cannabis use. The research included young people aged 5 to 42 years, with over 11,700 cannabis users and nearly 16,000 non-users serving as controls. The findings reveal a nuanced picture: consistent evidence shows that regular cannabis users experience declining IQ compared to non-users, with stronger effects linked to more frequent and persistent use patterns. Those who use cannabis more frequently also demonstrated worse executive function performance over time, suggesting that the dose and duration of use matter significantly.

However, the picture becomes more complicated when examining other cognitive domains. The review found mixed results for memory and learning abilities, with some studies showing deficits while others found no significant differences. Areas like processing speed, attention, and verbal comprehension showed minimal or insufficient evidence of cannabis-related changes. An important limitation is that most studies couldn't definitively establish whether cognitive problems existed before cannabis use began or were caused by the cannabis itself—a critical distinction that affects how we interpret the findings.

The research suggests that continued cannabis consumption, particularly at higher frequencies, may affect IQ and executive function over time, but the magnitude of these effects remains unclear. The authors emphasize the need for more studies examining vulnerable populations, the effects of stopping cannabis use, and whether cognitive changes differ based on cannabinoid profiles or consumption methods. These findings matter for young people considering or currently using cannabis, as they indicate potential long-term cognitive consequences worth weighing against other factors.

📄 Original Abstract

The regular consumption of cannabis has been associated with changes in cognition. However it is unclear how cognitive performance changes over time with continued cannabis use and whether cognitive alterations predate the onset of cannabis use. We conducted a narrative review of longitudinal observational naturalistic studies of cognition in people who use cannabis. We identified studies through PubMed and PsycINFO via the search terms "cannabis", "marijuana", "cognitive", and "cognition" and summarised findings by cognitive domain. The evidence included 21 studies of ~ 27,734 participants aged 5-to-42 years at baseline, comprising 11,783 people who consume cannabis - of which ~ 2,030 who were cannabis naïve at baseline and commenced consuming cannabis at later timepoints - and 15,951 controls. Consistent evidence (≥ 65% significant) showed: decreased IQ in the cannabis group vs. controls over time; associations between chronicity of use (e.g., persistent use/dependence, greater amount/frequency), lower IQ at distinct timepoints, and IQ decline over time; negative correlations between greater frequency of use at distinct timepoints and lower executive function; and negative correlations between increased frequency of use over time and decreases in executive function. There was mixed evidence (40%-to-60% significant) for differences between cannabis vs. control groups at individual timepoints and over time, for: verbal learning and memory, working/episodic memory, and perceptual reasoning. There was minimal evidence (≤ 35% significant) for cannabis use-related changes over time in verbal fluency/comprehension and processing speed, and insufficient evidence for attention. There was insufficient and mixed evidence from 6 studies comparing inconsistent cognitive domains prior to the onset of cannabis use, in cannabis naïve youth. Continued cannabis consumption over time and greater/increased frequency of cannabis use may affect performance in select domains of cognition. Evidence on how cognition changes in vulnerable people who use cannabis across the lifespan, and in relation to ceasing consumption is required.

Paper Type

📚 Review

Publication

Journal: Psychopharmacology
Published: May 11, 2026
PMID: 42108274
DOI: 10.1007/s00213-026-07072-1

Authors (6)

Gabrielle Abbott School of Psychology, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia.
Lisa-Marie Greenwood School of Medicine and Psychology, The Australian National University, Canberra, Australia.
Jessica G Bartschi School of Psychology, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia.
Antonio Verdejo-Garcia School of Psychological Sciences and Turner Institute for Brain and Mental Health, Monash University, Melbourne, Australia.
Nadia Solowij School of Psychology, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia.
+1 more authors