Cannabis plus nicotine was the worst substance combination for anxiety and wellbeing in young adults
Among 733 young adults in Montreal, the cannabis-nicotine combination was associated with the highest anxiety and lowest positive mental health, while no dose-response existed for number of substances.
Quick Facts
What This Study Found
No dose-response between substance count and mental health; cannabis-nicotine had strongest negative associations (anxiety b=2.58, PMH b=-5.90); alcohol-nicotine also linked to lower positive mental health.
Key Numbers
733 participants; 37% no regular use, 42% one, 16% two, 5% three; cannabis-nicotine: anxiety b=2.58 (1.06-4.10), PMH b=-5.90 (-10.04 to -1.76).
How They Did This
Cross-sectional analysis of 733 NDIT study participants (mean age 30.6); multivariable linear regression for regular alcohol, cannabis, and nicotine use patterns.
Why This Research Matters
Specific substance pairings matter more for mental health than total count, with cannabis-nicotine standing out as particularly problematic.
The Bigger Picture
Public health messaging should highlight specific combinations rather than simply counting substances.
What This Study Doesn't Tell Us
Cross-sectional; self-reported; single Canadian city; small subgroup sizes; reverse causation possible.
Questions This Raises
- ?Why is cannabis-nicotine particularly harmful?
- ?Is it pharmacological interaction or shared risk factors?
- ?Would cessation of one substance improve outcomes?
Trust & Context
- Key Stat:
- Cannabis-nicotine was the worst combination for anxiety and wellbeing
- Evidence Grade:
- Population-based cohort with specific combination analysis, but cross-sectional design limits causal interpretation.
- Study Age:
- Published 2025
- Original Title:
- Polysubstance use and mental health among young adults.
- Published In:
- Canadian journal of public health = Revue canadienne de sante publique, 116(6), 849-857 (2025)
- Authors:
- Chopra, Rajit, Sylvestre, Marie-Pierre(4), Pelekanakis, Annie, Doré, Isabelle, Omorou, Abdou Y, O'Loughlin, Jennifer
- Database ID:
- RTHC-06219
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does using more substances mean worse mental health?
Not in a simple dose-response way. The specific combination mattered more, with cannabis plus nicotine standing out as the worst pairing.
Which combination was most harmful?
Cannabis plus nicotine was associated with the highest anxiety and lowest positive mental health, worse than alcohol-nicotine or alcohol-cannabis.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-06219APA
Chopra, Rajit; Sylvestre, Marie-Pierre; Pelekanakis, Annie; Doré, Isabelle; Omorou, Abdou Y; O'Loughlin, Jennifer. (2025). Polysubstance use and mental health among young adults.. Canadian journal of public health = Revue canadienne de sante publique, 116(6), 849-857. https://doi.org/10.17269/s41997-025-01035-3
MLA
Chopra, Rajit, et al. "Polysubstance use and mental health among young adults.." Canadian journal of public health = Revue canadienne de sante publique, 2025. https://doi.org/10.17269/s41997-025-01035-3
RethinkTHC
RethinkTHC Research Database. "Polysubstance use and mental health among young adults." RTHC-06219. Retrieved from https://rethinkthc.com/research/chopra-2025-polysubstance-use-and-mental
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.