Supplementary Material for: A study of pupil response to light as a digital biomarker of recent cannabis use

Introduction: Given the roadside safety and occupational injury prevention implications associated with cannabis impairment, there is a need for objective and validated measures of recent cannabis use. Pupillary light response may offer an approach for detection.
Method: 84 participants (mean age: 32, 42% female) with daily, occasional, and no-use cannabis use histories participated in pupillary light response tests before and after smoking cannabis ad libitum or relaxing for 15 minutes (no use). The impact of recent cannabis consumption on trajectories of the pupillary light response was modeled using functional data analysis tools. Logistic regression models for detecting recent cannabis use were compared, and average pupil trajectories across cannabis use groups and times since light test administration were estimated.
Results: Models revealed small, significant differences in pupil response to light after cannabis use comparing the occasional use group to the no use control group, and similar statistically significant differences in pupil response patterns comparing the daily use group to the no use comparison group. Trajectories of pupillary light response estimated using functional data analysis found that acute cannabis smoking was associated with less initial and sustained pupil constriction compared to no cannabis smoking.
Conclusion: These analyses show the promise of pairing pupillary light response and functional data analysis methods to assess recent cannabis use.