In a controlled study, eyelid tremor showed poor specificity (18%) and was not significantly associated with recent cannabis smoking, undermining its use in drug recognition evaluations.
Law enforcement and policy makers involved in cannabis-impaired driving enforcement; researchers studying cannabis impairment biomarkers.
18% specificity for eyelid tremor as an indicator of recent cannabis use
What the researchers found
There was no significant association between recent cannabis use and eyelid tremor presence. Cannabis users were actually less likely to show tremors (OR: 0.75). The test had 86% sensitivity but only 18% specificity and 64% overall accuracy.
Why it matters
Eyelid tremor assessment is part of the Drug Evaluation and Classification Program used by law enforcement to identify cannabis-impaired drivers. This controlled study found it performs poorly as a diagnostic sign, with specificity so low that most positive results would be false positives.
The numbers in context
Sensitivity: 0.86. Specificity: 0.18. Accuracy: 0.64. Odds ratio for cannabis users having tremor: 0.75 (95% CI: 0.25-2.40). Inter-rater reliability: kappa 0.44-0.45, ICC 0.58-0.61 (moderate agreement).
How the study worked
Blinded, controlled study of 103 adults in three groups (daily users, occasional users, non-users). Eyelids were recorded by infrared videography before and approximately 71 minutes after cannabis smoking. Three trained expert observers (neuro-ophthalmology and toxicology) independently graded tremor without knowing use history or timing.
What this study cannot tell us
Eyelid recordings taken at only one post-smoking time point (70 minutes). Participants self-selected their cannabis products and doses due to regulatory restrictions. The study population was predominantly non-Hispanic White.
How to read the evidence
Moderate: well-designed blinded controlled study with expert observers, though limited to a single post-smoking time point and uncontrolled dosing.
When this study was published
2024 study.
The bigger picture
Accurately identifying cannabis impairment remains one of the biggest challenges in traffic safety. Unlike alcohol breathalyzers, no reliable roadside test exists for cannabis intoxication. This study adds to growing evidence that many current field sobriety markers for cannabis are scientifically unsupported.
Questions still open
- Would eyelid tremor perform differently at earlier time points after cannabis use (e.g., 15-30 minutes)? Are there other physiological signs that might serve as more reliable indicators of recent cannabis use?
Common questions
What is eyelid tremor used for?
Why is 18% specificity a problem?
Read the original research
Accuracy and replicability of identifying eyelid tremor as an indicator of recent cannabis smoking.
Clinical toxicology (Philadelphia, Pa.), 62(1), 10-18
Citation
Wang, George Sam; Kosnett, Michael; Subramanian, Prem; Wrobel, Julia; Ma, Ming; Brown, Tim; Bidwell, L Cinnamon; Brooks-Russell, Ashley. (2024). Accuracy and replicability of identifying eyelid tremor as an indicator of recent cannabis smoking.. Clinical toxicology (Philadelphia, Pa.), 62(1), 10-18. https://doi.org/10.1080/15563650.2024.2310154