evidence: Although a few authors have reported on the presence of cannabinoids in the milk of cannabis users, there are no studies reporting the effect of maternal cannabis use on breast milk composition.7,8,47 We report that maternal cannabis consumption during lactation is associated with the presence of several cannabinoids, including metabolites of THC, and attenuated IgA levels in the milk of users. This indicates that maternal cannabis consumption may impact an infant’s health due to direct cannabinoid exposure and altered milk composition. Further studies are needed to increase the body of evidence and to better inform mothers and the general population. [...] Ramnarine, R. S., Poklis, J. L. & Wolf, C. E. Determination of cannabinoids in breast milk using QuEChERS and ultra-performance liquid chromatography and tandem mass spectrometry. J. Anal. Toxicol.43, 746–752 (2019).