Field sobriety tests were poor at detecting cannabis impairment in heavy users
Standard Field Sobriety Tests were only mildly sensitive to cannabis impairment in heavy users, while a specific oral fluid device (Drager) showed high sensitivity for detecting THC.
Quick Facts
What This Study Found
Twenty heavy cannabis users participated in a placebo-controlled study where they smoked cannabis (400 micrograms/kg THC) with or without alcohol. Standard Field Sobriety Tests (SFST) were only mildly sensitive to cannabis-induced impairment.
Cannabis alone significantly affected performance on the one-leg stand test (p=0.037), but the overall SFST battery was poor at detecting impairment. The combination of cannabis and alcohol affected horizontal gaze nystagmus (p=0.029), but this test is primarily validated for alcohol.
For roadside drug detection, the Drager Drug Test 5000 demonstrated high sensitivity for detecting THC in oral fluid, while the Securetec Drugwipe 5 had low sensitivity. The results suggested different tools are needed for detecting cannabis impairment versus detecting cannabis presence.
Key Numbers
20 heavy cannabis users. THC dose: 400 micrograms/kg. Cannabis significantly affected one-leg stand (p=0.037). Cannabis + alcohol affected horizontal gaze nystagmus (p=0.029). Drager 5000: high THC sensitivity. Drugwipe 5: low sensitivity.
How They Did This
Double-blind, placebo-controlled study with 20 heavy cannabis users (15 males, 5 females, mean age 24.3). Participants received THC (400 micrograms/kg) with alcohol (targeting BAC 0.5 or 0.7 mg/mL) or placebo combinations. SFST performance and oral fluid THC detection were assessed.
Why This Research Matters
Field sobriety tests are the primary roadside tool for detecting impaired drivers. Their poor sensitivity to cannabis impairment means officers may not identify cannabis-impaired drivers, creating a gap in road safety enforcement.
The Bigger Picture
As cannabis legalization expanded, the inability of standard field sobriety tests to reliably detect cannabis impairment became a significant law enforcement and public safety challenge. Oral fluid testing offered a detection approach but detects presence, not necessarily impairment.
What This Study Doesn't Tell Us
Heavy users were tested, and tolerance likely reduced observable impairment. Time between cannabis use and testing may have affected results. The study could not determine whether the lack of SFST sensitivity reflected tolerance or genuine limitations of the tests for detecting cannabis effects.
Questions This Raises
- ?Should new field sobriety tests be developed specifically for cannabis?
- ?Does tolerance explain the poor SFST sensitivity, or are the tests inherently insensitive to cannabis effects?
- ?Can oral fluid THC levels reliably indicate impairment level?
Trust & Context
- Key Stat:
- Standard field sobriety tests were only mildly sensitive to cannabis
- Evidence Grade:
- Placebo-controlled study with relevant real-world application. Moderate sample size. Heavy user population may limit generalizability to occasional users.
- Study Age:
- Published in 2012. Cannabis-impaired driving detection remains a significant challenge. Newer devices and approaches have been developed but no gold standard exists.
- Original Title:
- A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid.
- Published In:
- Psychopharmacology, 223(4), 439-46 (2012)
- Authors:
- Bosker, W M, Theunissen, E L(6), Conen, S, Kuypers, K P C, Jeffery, W K, Walls, H C, Kauert, G F, Toennes, S W, Moeller, M R, Ramaekers, J G
- Database ID:
- RTHC-00545
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Can police tell if you are high from a field sobriety test?
This study found standard field sobriety tests were poor at detecting cannabis impairment in heavy users. These tests were designed and validated for alcohol, and cannabis produces different types of impairment that the tests are not well-suited to detect.
Can a test detect THC in saliva?
Yes, but detection and impairment are different things. The Drager Drug Test 5000 reliably detected THC in oral fluid, but having THC in saliva does not necessarily mean a person is impaired, especially in regular users who may have residual THC.
Read More on RethinkTHC
- cannabis-dependence-physical-psychological-addiction-science
- cannabis-perception-vs-evidence-gap
- cannabis-use-disorder-test
- cross-addiction-quit-weed-start-drinking
- is-weed-addictive
- is-weed-addictive-science
- quitting-weed-and-alcohol
- rehab-for-weed-addiction-necessary
- signs-of-cannabis-use-disorder
- weed-vape-pen-addiction
- pulled-over-with-weed-in-car
- being-high-247-brain-body-constant-thc
- optimal-tolerance-break-length-reset-timing
- what-happens-body-high-247-for-months
Cite This Study
https://rethinkthc.com/research/RTHC-00545APA
Bosker, W M; Theunissen, E L; Conen, S; Kuypers, K P C; Jeffery, W K; Walls, H C; Kauert, G F; Toennes, S W; Moeller, M R; Ramaekers, J G. (2012). A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid.. Psychopharmacology, 223(4), 439-46.
MLA
Bosker, W M, et al. "A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid.." Psychopharmacology, 2012.
RethinkTHC
RethinkTHC Research Database. "A placebo-controlled study to assess Standardized Field Sobr..." RTHC-00545. Retrieved from https://rethinkthc.com/research/bosker-2012-a-placebocontrolled-study-to
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.