Summary: A new study filled a critical diagnostic gap regarding substance use during the early warning phases of mental illness. Investigating adolescents and young adults at clinical high risk for psychosis, researchers demonstrated that the concurrent use of cannabis and tobacco, colloquially known as “co-use”, is associated with significantly lower cognitive performance compared to healthy controls.
By tracking data across a comprehensive battery of neuropsychological tests, the novel study provides clinicians with vital new risk indicators to shape early intervention strategies during the critical prodromal window before definitive psychotic symptoms fully develop.
Key Facts
- The Co-Use Epidemiological Surge: Dual consumption of cannabis and tobacco has steadily expanded over the past several decades, with one in five daily cigarette smokers aged 18 to 25 in the United States also meeting the criteria for daily cannabis use.
- The Prodromal Window Deficit: Cognitive impairment functions as one of the earliest measurable indicators of psychosis risk, emerging during the prodrome—the critical developmental window when early warning signs surface before a definitive diagnosis can be made.
- A Landmark Neurocognitive Audit: This represents the first study to explicitly evaluate how concurrent cannabis and tobacco use impacts neurocognitive metrics within an at-risk cohort, analyzing a dataset of 734 individuals at clinical high risk for psychosis and 278 healthy controls.
- Widespread Performance Drops: Utilizing data from the prospective North American Prodrome Longitudinal Study 2, lead investigator Dr. Heather Burrell Ward observed that at-risk individuals who co-used both substances over the past month exhibited lower scores across a broad range of neuropsychological tests compared to healthy controls.
- The Non-User Social Paradox: Surprisingly, at-risk individuals who reported zero substance use also demonstrated lower cognitive performance, paired with the absolute lowest scores in social functioning across the entire cohort.
- The Isolated Adolescent Subtype: Co-investigator Dr. Ricardo E. Carrión explains that these non-using, at-risk youth likely represent a distinct, socially impaired subtype; because adolescent substance use is heavily tied to peer networking, individuals with severe social deficits simply have fewer opportunities to engage in co-use.
- Clinical Screening Mandate: Given that causality and directionality remain unknown, Editor-in-Chief Dr. Cameron S. Carter and the research team advise that clinicians working with vulnerable youth must routinely screen for concurrent tobacco and cannabis use to build comprehensive adolescent mental health frameworks.
Source: Elsevier
New research shows that among people at clinical high risk for psychosis, cannabis and tobacco co-use was associated with lower cognitive performance compared to healthy controls.
The novel study appearing in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, published by Elsevier, fills a critical gap in research, providing clinicians and scientists with vital new insights into the risks associated with cannabis and tobacco co-use and the potential impact on vulnerable adolescents.
Use of both cannabis and tobacco (known as “co-use”) has been on the rise in the general population for the past several decades. Of individuals aged 18-25 in the United States, one in five daily cigarette smokers is also a daily cannabis user. In the general population, co-use is associated with an increased risk for any mental health disorder. People with psychotic disorders have a very high prevalence of both tobacco and cannabis use, but information on co-use in this population is lacking.
This is the first study to investigate cannabis and tobacco co-use and neurocognitive performance in this population. Researchers analyzed data from 734 individuals at clinical high risk for psychosis and 278 healthy controls taking part in the multisite prospective North American Prodrome Longitudinal Study 2.
“Prior research investigating tobacco and cannabis use in people with psychotic disorders has been mixed, showing associations with better cognitive performance in some cases and worse in others,” notes Editor-in-Chief of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging Cameron S. Carter, MD, University of California Irvine School of Medicine.
“Impaired cognitive performance is one of the earliest indicators of psychosis risk. Until now, there had been no studies examining the effects of co-use on cognitive performance in the psychosis population or in the prodrome—the critical early window when warning signs emerge before definitive illness-specific symptoms develop.”
Lead investigator Heather Burrell Ward, MD, Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, says, “In this study individuals at clinical high risk for psychosis reported their substance use over the past month and completed a comprehensive battery of neuropsychological testing. Across a broad range of cognitive tests, we observed that at-risk individuals who used both cannabis and tobacco performed worse on cognitive testing compared to healthy controls.”
The researchers were surprised to find that individuals at risk for psychosis who reported that they did not use any substances also had lower cognitive performance and the lowest social function.
“We found that at-risk individuals who had not used any substances may represent a distinct, socially impaired subtype,” explains co-investigator Ricardo E Carrión, PhD, Institute for Behavioral Science, Feinstein Institutes for Medical Research, Northwell Health System, and Department of Psychiatry, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell. “Because these are adolescents and substance use is often linked to social interactions, those who are less social simply may not have as much opportunity to engage in substance use.”
While these findings offer important insights, causality remains unknown. Future studies should investigate associations over time between frequency of cannabis and tobacco use and neurocognitive performance to untangle the directionality of these links. Also, clinicians working with at-risk youth should regularly ask about co-use of tobacco and cannabis.
Dr. Ward concludes, “This research is especially important as the prevalence of cannabis and tobacco co-use in the general population is rising. It is crucial to understand the impact of this co-use in people at clinical high risk for psychosis—a period during adolescence when individuals may start to show attenuated psychotic symptoms and when substance use often begins. Our findings can inform early intervention and a more comprehensive approach to adolescent mental health.”
Key Questions Answered:
A: Because the prodrome represents the early warning window where cognitive problems first appear before definitive psychotic symptoms fully develop. Since adolescence is when both substance use and early psychiatric warning signs typically emerge, mapping this specific window helps doctors intercept risks before they spiral into permanent conditions.
A: Because adolescent substance use is deeply intertwined with peer groups and social interactions. Teenagers at high risk for psychosis who struggle with severe social impairments are often so isolated that they simply lack the peer opportunities or social circles where substance co-use takes place.
A: To stop treating tobacco and cannabis as separate, low-priority habits and regularly screen for concurrent co-use. Since dual use is rising rapidly among young adults and is tied to lower cognitive performance in vulnerable minds, clinicians must catch co-use early to build effective mental health interventions.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this cognition and psychosis research news
Author: Eileen Leahy
Source: Elsevier
Contact: Eileen Leahy – Elsevier
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Cannabis and Tobacco Co-Use Is Associated with Impaired Neurocognitive Performance in Individuals at Clinical High Risk for Psychosis” by Fatemeh Keyvani, Luisa M. Muller, Natalie Fudge, Bridget MacLean, Agosh Saini, Joshua Khatri, Thomas Kriesen, Matthias Wittstock, Florian A. Gessler, Robert Langer, Joshua D. Bernstock, Shriya Srinivasan, and Mahla Poudineh. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging
DOI:10.1016/j.bpsc.2026.03.021
Abstract
Cannabis and Tobacco Co-Use Is Associated with Impaired Neurocognitive Performance in Individuals at Clinical High Risk for Psychosis
Background
Cannabis use is highly prevalent among people with psychotic disorders. While there is some indication that cannabis use exacerbates psychosis symptoms, its neurocognitive effects remain unclear. Co-use of cannabis and tobacco is increasing in the general population, but little is known about its effects in people with psychosis or those at risk of developing a psychotic disorder, including its effects on cognitive performance.
Methods
We analyzed data from the North American Prodrome Longitudinal Study 2, a multi-site prospective study of individuals at clinical high risk for psychosis (CHR-P) and healthy controls. Cognitive performance was assessed using the MATRICS Consensus Cognitive Battery and the Seidman Auditory Continuous Performance Task. We examined differences in cognitive performance across 6 study groups: 1) CHR-P tobacco use, 2) CHR-P cannabis use, 3) CHR-P co-use, 4) CHR-P who did not use tobacco or cannabis, 5) CHR-P who did not use substances, and 6) healthy controls.
Results
Among 1,012 participants (734 CHR-P, 278 healthy controls), co-use of cannabis and tobacco was associated with lower global cognitive performance and lower working memory, verbal learning, and attentional performance compared to healthy controls. CHR-P individuals who did not use substances also had lower cognitive performance across multiple measures, including global cognition, working memory, verbal learning, visual learning, and attentional performance. The CHR-P non-substance use group also had the lowest social function.
Conclusions
Cannabis and tobacco co-use is associated with lower neurocognitive performance, which may explain the mixed associations between cannabis use and cognitive performance in previous literature.
