Introduction: Research on the associations between prenatal cannabis use and infant health outcomes are limited by sub-optimal measurement of cannabis exposure; which increases misclassification bias. Existing measurement options fail to account for the frequency, timing, dose and mode of cannabis consumption, and may be susceptible to biased responses in pregnancy. Objective: To develop and validate an antenatal cannabis use measurement tool that addresses measurement limitations in previous studies, using patient-oriented, peer-reviewed methods.
Methods: We conducted in-depth individual qualitative interviews (IDI) with pregnant cannabis users, and devised items from the resulting themes and language used. We assessed the potential for biased response to each item to reduce their bias-potential, using in-depth cognitive interviewing with additional pregnant women. (10 users, 2 non-users) We tested the final tool for convergent and discriminant validity, split-half and test-retest reliability in 162 pregnant Albertans.
Results: IDIs reached theoretical saturation after 8 interviews and results informed the inclusion and wording of a tool preamble, 5 specific wording choices (e.g. use vs. consume; medicinal vs. medical), 6 preferred response options, and the structure of 2 items. Cognitive interviews were saturated after 12 interviews (10 users, 2 non-users), and resulted in 15 revisions of the tool to eliminate participant-perceived sources of response-bias. The final tool has 9 items measuring reasons for antenatal cannabis use; timing, frequency, dose, and mode(s) of consumption, and exposure to second-hand smoke and vapor. It showed excellent discriminant validity against published substance-use-disorder screening tools (R= –0.27-0.15), and convergent validity against IDIs (R=0.73-1.0). Internal consistency (R=0.69-0.90), and test-retest reliability (R=0.92, P=0.013) were also high.
Conclusion: The CEPT is the first validated measure of antenatal cannabis use for research purposes. It addresses limitations of previously available measurement options. It has the potential to improve the quality of prospective research on antenatal cannabis exposures and associated maternal and infant health outcomes.
Carly McMorris– Assistant Professor, University of Calgary
Amy Metcalfe– Associate Professor, University of Calgary
Stephen Wood– Associate Professor, Alberta Health Services, University of Calgary
Catherine Ringham– Post-Doctoral Fellow, University of Calgary
Sheila McDonald– Research Scientist - Maternal Child Health, Alberta Health Services