Summary: A new study addresses a crucial diagnostic gap by examining how combined cannabis and tobacco use affects cognition during the prodromal period of psychosis. In adolescents and young adults identified as clinical high risk for psychosis (CHR-P), concurrent use of cannabis and tobacco—commonly called “co-use”—was linked with significantly poorer neurocognitive performance compared with healthy controls.
Using a comprehensive neuropsychological battery, the study identifies substance co-use as a potential clinical indicator that can help clinicians refine early intervention and prevention efforts during the prodrome, the sensitive window before full-blown psychotic illness appears.
Key Facts
- Rising Co-Use: Dual use of cannabis and tobacco has increased over recent decades. Among US individuals aged 18–25, a substantial proportion of daily cigarette smokers also report daily cannabis use.
- Prodromal Cognitive Decline: Cognitive impairments often appear early in the prodrome and can signal elevated risk for psychosis before diagnostic criteria are met.
- Largest Neurocognitive Assessment to Date: This is the first study to directly evaluate the impact of cannabis and tobacco co-use on cognitive functioning in a CHR-P cohort, analyzing data from 734 at-risk participants and 278 healthy controls.
- Widespread Cognitive Effects: Data from the North American Prodrome Longitudinal Study 2 (NAPLS2) show that CHR-P individuals reporting co-use in the previous month had lower scores across multiple cognitive domains compared with healthy controls.
- Unexpected Non-User Pattern: CHR-P participants who reported no substance use also displayed lower cognitive performance and the poorest social functioning within the sample, suggesting a possible distinct subgroup characterized by social isolation.
- Clinical Screening Recommendation: Although causality remains unresolved, the research team recommends routine screening for concurrent cannabis and tobacco use among adolescents and young adults at elevated clinical risk for psychosis to support comprehensive care planning.
Source: Elsevier
New findings show that cannabis and tobacco co-use in people at clinical high risk for psychosis is associated with lower cognitive performance compared with healthy controls.
Published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, the study fills an important research gap by clarifying how combined tobacco and cannabis use relates to cognitive functioning in vulnerable youth. Prior literature on cannabis use and cognition in psychosis has been inconsistent, with some studies reporting better performance and others worse; this analysis helps explain why those differences may exist.
Co-use of cannabis and tobacco is increasingly common in the general population and is linked to elevated risk for mental health problems. People with psychotic disorders traditionally show high rates of tobacco and cannabis use, but detailed information about the cognitive implications of co-use in those at risk had been lacking until now.
Lead investigator Heather Burrell Ward, MD, and colleagues analyzed self-reported substance use over the previous month and a broad battery of neuropsychological tests. Compared with healthy controls, CHR-P participants who reported co-use performed worse across domains including working memory, verbal learning, and attention.
Co-investigator Ricardo E. Carrión, PhD, notes that CHR-P participants who reported no substance use may represent a socially impaired subgroup. Because adolescent substance use often occurs within peer networks, youth with severe social deficits may have fewer opportunities to engage in co-use and may therefore present with different clinical and cognitive profiles.
While these findings are clinically meaningful, they do not establish cause and effect. The authors call for longitudinal research tracking frequency and duration of tobacco and cannabis use alongside repeated neurocognitive testing to determine how substance use and cognitive decline influence one another over time. In the meantime, clinicians working with at-risk adolescents should routinely assess for concurrent use of tobacco and cannabis as part of comprehensive risk evaluation.
Dr. Ward emphasizes the public health importance of the findings: the increasing prevalence of cannabis and tobacco co-use among young people makes it essential to understand its potential effects during adolescence, a period when early psychotic symptoms often first appear and when substance use typically begins. These results can inform early intervention strategies and broaden adolescent mental health care to address combined substance use.
Key Questions Answered:
A: The prodrome is the early warning period when cognitive decline and other subtle signs first appear before definite psychotic symptoms develop. Since adolescence is the typical onset for both substance use and early psychiatric symptoms, focusing on this window helps clinicians identify and intervene on risk factors sooner.
A: Adolescent substance use is frequently social. Youth with severe social impairments may be more isolated and therefore less likely to engage in peer-driven behaviors like co-use, marking them as a potentially distinct clinical subgroup with increased social and cognitive vulnerabilities.
A: Clinicians should consider screening routinely for concurrent cannabis and tobacco use rather than treating them as separate low-priority behaviors. Dual use is rising and appears linked to lower cognitive performance in vulnerable adolescents, so early detection can support better-targeted interventions.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The original journal article was reviewed in full.
- Additional context and clarification were added by editorial 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 Daniel Bello et al., 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 common among people with psychotic disorders, and combined use with tobacco has grown in the general population. The effect of cannabis on cognitive functioning in psychosis and prodromal groups has been inconsistent in past studies, and little is known about how co-use specifically affects cognitive performance in those at heightened risk for psychosis.
Methods
Researchers analyzed data from the North American Prodrome Longitudinal Study 2, a multi-site prospective cohort including individuals at clinical high risk for psychosis (CHR-P) and healthy controls. Cognitive performance was measured with the MATRICS Consensus Cognitive Battery and the Seidman Auditory Continuous Performance Task. Participants were classified into six groups based on tobacco and cannabis use patterns, including CHR-P co-use, single-substance use, non-use, and healthy controls.
Results
Among 1,012 participants (734 CHR-P, 278 healthy controls), co-use of cannabis and tobacco was associated with lower global cognition and reduced performance in working memory, verbal learning, and attention relative to healthy controls. CHR-P participants who reported no substance use also displayed lower cognitive scores across several domains and the lowest social functioning, suggesting heterogeneous clinical subtypes within the at-risk group.
Conclusions
Cannabis and tobacco co-use is associated with impaired neurocognitive performance in individuals at clinical high risk for psychosis. These findings help explain prior conflicting reports about cannabis and cognition in psychosis and emphasize the need for longitudinal research and routine screening for co-use in adolescent mental health care.