Adolescents who used nicotine and cannabis on the same day had over 4 times the odds of cannabis dependence symptoms compared to those who used both but on different days.
Adolescent substance use researchers, school counselors, and prevention program designers.
Same-day nicotine-cannabis use was associated with 4.28x higher odds of cannabis dependence symptoms
What the researchers found
Among 3,823 Southern California high school students, 3.3% reported same-day nicotine-cannabis co-use. Same-day co-users had 4.28 times the odds of cannabis dependence symptoms (95% CI: 1.98-9.28) compared to those who used both substances in the same month but not on the same day. Odds of nicotine dependence were also elevated (aOR=1.81) but not statistically significant.
Why it matters
This study demonstrates that how researchers measure co-use matters. Same-day co-use appears to be a marker of more problematic behavior than simply using both substances within the same month.
The numbers in context
3,823 students. 3.3% same-day co-use, 1.5% past-month co-use, 1.6% exclusive nicotine, 3.1% exclusive cannabis, 90.5% no use. Same-day vs past-month co-use: cannabis dependence aOR=4.28 (95% CI: 1.98-9.28). Nicotine dependence aOR=1.81 (95% CI: 0.87-3.77, NS).
How the study worked
Cross-sectional survey of 3,823 Southern California high school students in Fall 2022. Five mutually exclusive past-month use groups. Adjusted logistic regression models for nicotine and cannabis dependence symptoms.
What this study cannot tell us
Cross-sectional design. Southern California sample may not generalize. Self-reported use and dependence symptoms. Small absolute numbers in co-use groups limit statistical power. Cannot determine if same-day use causes dependence or if more dependent users are more likely to co-use.
How to read the evidence
Reasonable sample with precise co-use measurement, but cross-sectional design and regional sample limit causal inference.
When this study was published
2025 publication with Fall 2022 data.
The bigger picture
Combined with the adult finding that simultaneous alcohol-cannabis use is riskier than concurrent use (RTHC-06681), this study reinforces that the temporal pattern of substance co-use is a critical but often overlooked dimension of risk.
Questions still open
- Does same-day co-use cause more dependence, or do more dependent teens simply use more substances on any given day?
- Would interventions targeting same-day co-use specifically reduce dependence trajectories?
Read the original research
Assessment of nicotine and cannabis co-use among adolescents and the association with nicotine and cannabis dependence symptoms.
Addictive behaviors, 171, 108471
Citation
Jafarzadeh, Nikki S; Harlow, Alyssa F; Walsh, Claire A; Whaley, Reid C; Han, Dae-Hee; Leventhal, Adam M; Barrington-Trimis, Jessica L. (2025). Assessment of nicotine and cannabis co-use among adolescents and the association with nicotine and cannabis dependence symptoms.. Addictive behaviors, 171, 108471. https://doi.org/10.1016/j.addbeh.2025.108471
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