Summary: New research closes a crucial diagnostic gap about substance use during the early warning stages of mental illness. In adolescents and young adults identified as being at clinical high risk for psychosis, concurrent use of cannabis and tobacco—commonly called “co-use”—was linked to notably poorer cognitive performance compared with healthy control participants.
Using an extensive battery of neuropsychological tests, this study supplies clinicians with important risk markers that can inform early intervention during the prodromal window, the period when subtle signs of psychosis first emerge before a definitive diagnosis is possible.
Key Facts
- Rising Co-Use: Dual consumption of cannabis and tobacco has increased steadily over recent decades. In the United States, about one in five daily cigarette smokers aged 18–25 also report daily cannabis use.
- Prodromal Cognitive Decline: Cognitive impairment is among the earliest measurable signs of psychosis risk, appearing in the prodromal phase when early warning symptoms are present but a full diagnosis has not yet formed.
- A First-of-its-Kind Neurocognitive Review: This is the first study to directly evaluate how cannabis and tobacco co-use affects neurocognitive performance in a cohort at clinical high risk for psychosis, analyzing 734 at-risk individuals and 278 healthy controls.
- Broad Cognitive Deficits with Co-Use: Using data from the multisite North American Prodrome Longitudinal Study 2 (NAPLS-2), investigators observed that at-risk participants who reported using both cannabis and tobacco in the prior month scored lower across a wide range of cognitive measures than healthy controls.
- Non-User Social Subtype: Unexpectedly, at-risk participants who reported no substance use also exhibited reduced cognitive function and had the lowest social functioning scores of any subgroup in the sample.
- Social Isolation May Explain Non-Use: Co-investigator Dr. Ricardo E. Carrión suggests that non-using at-risk adolescents may form a distinct socially impaired subtype; because adolescent substance use is often social, those with marked social deficits may simply have fewer opportunities to engage in co-use.
- Clinical Screening Recommended: Although this study does not establish causality or directionality, the editorial team and researchers advise clinicians who work with vulnerable youth to routinely screen for concurrent cannabis and tobacco use as part of comprehensive adolescent mental health care.
Source: Elsevier
New findings indicate that cannabis and tobacco co-use in individuals at clinical high risk for psychosis is associated with lower cognitive performance compared to healthy controls.
Published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, this study addresses an important knowledge gap by clarifying how simultaneous cannabis and tobacco use may relate to neurocognitive function among adolescents and young adults vulnerable to psychosis.
Co-use of cannabis and tobacco has become more common in the general population. Prior research has linked co-use with heightened risk for mental health disorders, and people with psychotic disorders show high rates of both tobacco and cannabis consumption. However, prior to this work, little direct evidence existed on how co-use affects cognition in those at clinical high risk for psychosis.
Researchers examined data from 1,012 participants in the North American Prodrome Longitudinal Study 2: 734 individuals at clinical high risk for psychosis (CHR-P) and 278 healthy controls. Substance use over the previous month was assessed and participants completed a comprehensive neuropsychological battery.
“Previous studies of tobacco and cannabis in people with psychotic disorders have produced mixed results—some showing better cognitive performance, others worse,” said Cameron S. Carter, MD, editor-in-chief of the journal. “Because impaired cognition is an early marker of psychosis risk and the prodromal phase is a crucial early window, understanding how co-use affects cognition in this population was a key unmet need.”
Lead investigator Heather Burrell Ward, MD, described the findings: participants at clinical high risk who reported both cannabis and tobacco use in the past month showed lower performance across global cognition and several cognitive domains compared with healthy controls. Declines were particularly notable in working memory, verbal learning, and attention measures.
The team also observed that CHR-P participants who reported no substance use nevertheless had reduced cognitive performance across multiple domains and the lowest social functioning among all groups. “That non-using group may reflect a distinct, socially isolated subtype,” noted co-investigator Ricardo E. Carrión, PhD. “Adolescent substance use is often social—those who are most isolated may lack the peer networks where co-use occurs.”
While these results clarify associations, they do not determine whether co-use causes cognitive decline or whether existing cognitive or social deficits influence substance patterns. The authors recommend longitudinal studies to assess how frequency and duration of co-use relate to changes in neurocognitive performance over time. In the meantime, clinicians treating at-risk youth are urged to include routine screening for concurrent cannabis and tobacco use.
Dr. Ward emphasized the clinical relevance: “As cannabis and tobacco co-use rises in the general population, it is important to understand its potential impact during adolescence—a developmental period when attenuated psychotic symptoms may emerge and substance use often begins. These findings can inform targeted early interventions and a more complete approach to adolescent mental health.”
Key Questions Answered:
A: The prodrome is the early warning period when cognitive difficulties often first appear before full-blown psychotic symptoms. Because adolescence is when both substance use and early psychiatric signs typically begin, studying this window helps clinicians detect and address risks earlier.
A: Adolescent substance use is frequently tied to peer networks and social activity. Teens at high risk for psychosis who have severe social impairments may be more isolated and therefore less likely to participate in social behaviors that include substance co-use.
A: Treat tobacco and cannabis co-use as clinically relevant risk factors. Given rising rates of dual use and its association with poorer cognitive performance in vulnerable youth, clinicians should routinely screen for concurrent use and incorporate findings into prevention and early intervention plans.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was provided by 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, Jillian G. Connolly, Jean Addington, Carrie E. Bearden, Kristin Cadenhead, Tyrone D. Cannon, Barbara Cornblatt, Matcheri Keshavan, Daniel H. Mathalon, Diana O. Perkins, Larry Seidman, William S. Stone, Ming T. Tsuang, Elaine F. Walker, Scott Woods, Roscoe O. Brady Jr., Ricardo E. Carrión, and Heather Burrell Ward. 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 some evidence suggests cannabis may worsen psychosis symptoms. The neurocognitive effects of cannabis, however, are not fully clear. Co-use of cannabis and tobacco is increasing, yet its impact on cognition in people with psychosis or those at elevated risk is poorly understood.
Methods
This analysis used 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 measured with the MATRICS Consensus Cognitive Battery and the Seidman Auditory Continuous Performance Task. Participants were grouped into six categories based on recent tobacco and cannabis use and compared across cognitive domains.
Results
Among 1,012 participants (734 CHR-P, 278 healthy controls), co-use of cannabis and tobacco was linked to lower global cognition and poorer performance in working memory, verbal learning, and attention relative to healthy controls. CHR-P participants who reported no substance use also showed reduced performance across several cognitive measures and had the lowest social functioning scores.
Conclusions
Cannabis and tobacco co-use is associated with diminished neurocognitive performance in individuals at clinical high risk for psychosis, a finding that may help reconcile inconsistent results in prior studies of cannabis and cognition. Longitudinal research is needed to determine causality and the direction of these associations.