Researchers tried to build a phone-based THC impairment test and it mostly didn't work
THC impaired performance on standard computer-based cognitive tasks but most phone-based equivalents failed to detect the impairment, raising doubts about the feasibility of a phone app as a cannabis field sobriety test.
Quick Facts
What This Study Found
Across two double-blind studies with oral THC (7.5 and 15 mg), standard computer tasks detected impairment in cognitive speed, reaction time, and working memory. However, most brief phone-based versions of the same tasks did not detect THC-induced impairment.
Key Numbers
Two studies, n=24 each. THC doses: 7.5 mg and 15 mg oral. Computer tasks detected impairment; most phone tasks did not.
How They Did This
Two double-blind, within-subjects studies (n=24 each) with healthy non-daily cannabis users. Participants received oral THC capsules (0, 7.5, 15 mg) in three sessions. At peak drug effect, they completed both standard computer-based cognitive tasks and brief phone-based tasks measuring speed, reaction time, fine motor ability, working memory, and time perception.
Why This Research Matters
Unlike alcohol breathalyzers, there is no reliable quick test for cannabis impairment. This study shows how difficult it is to compress cognitive testing into a brief, phone-friendly format sensitive enough to detect THC effects.
The Bigger Picture
Law enforcement and employers want a practical way to test for cannabis impairment, similar to alcohol breathalyzers. This research suggests that simple phone-based apps may be too brief and insensitive to fill that role.
What This Study Doesn't Tell Us
Small sample sizes (24 per study). Only oral THC was tested; smoked or vaped cannabis may produce different impairment patterns. The phone tasks were prototypes, not a fully developed app.
Questions This Raises
- ?Could longer or more complex phone tasks achieve sufficient sensitivity?
- ?Would combining multiple brief measures into a composite score improve detection?
- ?How does oral THC impairment compare to inhaled THC impairment on these measures?
Trust & Context
- Key Stat:
- Most phone tasks failed to detect THC impairment
- Evidence Grade:
- Moderate: two randomized, double-blind, placebo-controlled studies, but small sample sizes and prototype measures.
- Study Age:
- Published in 2019.
- Original Title:
- Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol.
- Published In:
- Journal of psychopharmacology (Oxford, England), 33(9), 1160-1169 (2019)
- Authors:
- Pabon, Elisa(2), de Wit, Harriet(5)
- Database ID:
- RTHC-02216
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Why is building a cannabis impairment test so hard?
Cannabis impairment varies widely between individuals and depends on tolerance, dose, and method of consumption. Unlike alcohol, blood THC levels don't correlate well with actual impairment, making objective testing extremely challenging.
Could a phone app ever work for this?
Possibly, but it would likely need to be more extensive than the brief tasks tested here. The researchers suggested that the brevity needed for real-world use may inherently sacrifice sensitivity.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02216APA
Pabon, Elisa; de Wit, Harriet. (2019). Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol.. Journal of psychopharmacology (Oxford, England), 33(9), 1160-1169. https://doi.org/10.1177/0269881119862533
MLA
Pabon, Elisa, et al. "Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol.." Journal of psychopharmacology (Oxford, 2019. https://doi.org/10.1177/0269881119862533
RethinkTHC
RethinkTHC Research Database. "Developing a phone-based measure of impairment after acute o..." RTHC-02216. Retrieved from https://rethinkthc.com/research/pabon-2019-developing-a-phonebased-measure
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.