Human Milk Cannabinoid Concentrations and Associations with Maternal Factors: The Lactation and Cannabis (LAC) Study
Elizabeth A. Holdsworth, Anna Berim, David R. Gang, Janet E. Williams, Caroline B. Smith, Beatrice Caffé, Olivia Brooks, Celestina Barbosa‐Leiker, Mark A. McGuire, Shelley McGuire, Courtney L. Meehan
Abstract
Background and Objectives: As cannabis use increases among reproductive-aged women, there is a growing need to better understand the presence of cannabinoids in milk produced by women using cannabis. It is unclear how concentrations of cannabinoids such as delta-9-tetrahydrocannabinol (Δ 9 -THC) persist in milk after cannabis use and what factors contribute to variation in milk Δ 9 -THC concentrations. Our objectives were to measure cannabinoids in human milk following cannabis abstention, after single and repeated instances of cannabis use, and identify factors contributing to concentration variation. Methods: The Lactation and Cannabis (LAC) Study prospectively observed 20 breastfeeding participants who frequently used cannabis (≥1/week), had enrolled <6 months postpartum, were feeding their infant their milk ≥5 times/day, and were not using any illicit drugs. Participants collected a baseline milk sample after ≥12 hours of abstaining from cannabis and five milk samples at set intervals over 8–12 hours after initial cannabis use. Participants completed surveys and recorded self-directed cannabis use during the study period. Results: Δ 9 -THC peaked 120 minutes after a single instance of cannabis use (median, n = 9). More instances of cannabis use during the study period were associated with greater Δ 9 -THC area-under-the-curve concentrations (ρ = 0.65, p = 0.002), indicating Δ 9 -THC bioaccumulation in most participants. Baseline Δ 9 -THC logged concentration was positively associated with self-reported frequency of cannabis use ( b = 0.57, p = 0.01). Conclusions: Cannabinoids are measurable in human milk following cannabis use, and concentrations remain elevated with repeated cannabis use over a day. Substantial variation in Δ 9 -THC milk concentrations reflects individual differences in characteristics and behavior, including average postpartum frequency of cannabis use.