Validity of Self-Reported Cannabis Use Based on Urine Toxicology Measures in a Population-Based Pregnancy Cohort in Michigan

BACKGROUND: Prenatal cannabis use may be underreported due to social stigma and fear of legal repercussions. The study assesses the validity of self-reported prenatal cannabis use versus urine toxicology measures and determines correlates of non-disclosure. METHODS: Data are from a statewide population-based pregnancy cohort (MARCH- Michigan Archive for Research on Child Health). Participants were recruited at first prenatal visit from 22 clinics in 2017-2023. We calculated sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) of self-reported cannabis use using urine toxicology as the criterion standard. RESULTS: 606 participants who self-reported cannabis use data within 30 days of urine collection were considered for analysis. Self-reports identified a prevalence of 14.2% for prenatal cannabis use, whereas urinalysis prevalence was 19.1%. Sensitivity, specificity, PPV, and NPV of self-report were 57.8%, 96.1%, 77.9% and 90.6%, respectively. No significant differences were observed between participants who disclosed and those who did not, except for race and ethnicity. The sensitivity of self-reports among Non-Hispanic Blacks was 45.5% compared to 73.0% for their non-Hispanic White counterparts. CONCLUSIONS: Self-reports can underestimate prenatal cannabis use especially among disadvantaged populations. The use of biospecimens to assess cannabis exposure is warranted for reducing misclassification and improving validity in research studies.