Drivers with alcohol interlock devices increased cannabis use, and it persisted after device removal

Drivers who cut alcohol use while an interlock device was installed significantly increased cannabis use, and that increase continued even after the device was removed.

Scherer, Michael et al.·Journal of studies on alcohol and drugs·2022·Moderate EvidenceLongitudinal Cohort
RTHC-04199Longitudinal CohortModerate Evidence2022RETHINKTHC RESEARCH DATABASErethinkthc.com/research

Quick Facts

Study Type
Longitudinal Cohort
Evidence
Moderate Evidence
Sample
N=189

What This Study Found

Among 189 DUI-convicted drivers, those who decreased alcohol use while an ignition interlock device was installed significantly increased cannabis use, which continued to rise after the device was removed.

Key Numbers

189 participants completed all three waves. Cannabis use increased across the study period overall. Drivers who decreased alcohol during IID use significantly increased cannabis, with further increases after device removal.

How They Did This

Three-wave longitudinal study of 189 New York State DUI-convicted drivers from 2015 to 2020. Oral fluid and blood samples measured cannabis use; hair samples measured alcohol use. Assessed at IID installation, removal, and 6-month follow-up.

Why This Research Matters

Alcohol interlock devices effectively prevent drunk driving, but this study reveals an unintended consequence: some drivers substitute cannabis for alcohol, creating a different impairment risk.

The Bigger Picture

This finding highlights the concept of substance substitution in impaired driving interventions. Preventing one type of impaired driving may inadvertently increase another.

What This Study Doesn't Tell Us

Sample size was moderate at 189. The study was conducted in New York State, which may limit generalizability. Self-selection effects may be at play, as those who reduce alcohol may already be predisposed to use other substances.

Questions This Raises

  • ?Would adding cannabis monitoring to IID programs reduce this substitution effect?
  • ?Do drivers who increase cannabis use also drive while impaired by cannabis?
  • ?Could counseling during IID installation prevent substance switching?

Trust & Context

Key Stat:
Cannabis use continued rising even after the interlock device was removed
Evidence Grade:
Moderate: three-wave longitudinal design with biological measures, but moderate sample size and observational design.
Study Age:
Published in 2022.
Original Title:
Cannabis Adaptation During and After Alcohol Ignition Interlock Device Installation: A Longitudinal Study.
Published In:
Journal of studies on alcohol and drugs, 83(4), 486-493 (2022)
Database ID:
RTHC-04199

Evidence Hierarchy

Meta-Analysis / Systematic Review
Randomized Controlled Trial
Cohort / Case-ControlFollows or compares groups over time
This study
Cross-Sectional / Observational
Case Report / Animal Study

Follows a group of people over time to track how outcomes develop.

What do these levels mean? →

Frequently Asked Questions

What is an alcohol ignition interlock device?

It prevents a car from starting if the driver's breath alcohol exceeds 0.025%. It is commonly mandated for DUI-convicted drivers.

Did all drivers increase cannabis use?

No. The significant increase was specifically among drivers who decreased their alcohol use while the device was installed, suggesting a substitution pattern rather than a universal effect.

What are the policy implications?

The researchers recommend supplemental treatment interventions during IID installation to address the potential for substance switching and polysubstance use.

Read More on RethinkTHC

Cite This Study

RTHC-04199·https://rethinkthc.com/research/RTHC-04199

APA

Scherer, Michael; Romano, Eduardo; King, Sagan; Marques, Paul; Romosz, Ann; Taylor, Eileen; Nochajski, Thomas H; Voas, Robert; Manning, Amy; Tippetts, Scott. (2022). Cannabis Adaptation During and After Alcohol Ignition Interlock Device Installation: A Longitudinal Study.. Journal of studies on alcohol and drugs, 83(4), 486-493.

MLA

Scherer, Michael, et al. "Cannabis Adaptation During and After Alcohol Ignition Interlock Device Installation: A Longitudinal Study.." Journal of studies on alcohol and drugs, 2022.

RethinkTHC

RethinkTHC Research Database. "Cannabis Adaptation During and After Alcohol Ignition Interl..." RTHC-04199. Retrieved from https://rethinkthc.com/research/scherer-2022-cannabis-adaptation-during-and

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.