Use of cannabis impacts breast milk and lactation, finds study

The prevalence of cannabis use has been reported to increase by over 62% among pregnant women. Fewer women of reproductive age believe that cannabis use is dangerous, with many considering it medicinal, more effective, and less toxic than many medications, prescription or otherwise, for morning sickness. Lactating women often cite conditions like anxiety, depression, nausea, loss of appetite, chronic pain, and posttraumatic stress disorder as reasons for their cannabis use. The fetus is exposed to maternally absorbed cannabis and its metabolites. Previous studies have shown a loss of verbal aptitude, attention, and short-term memory in fetuses exposed to cannabis in utero.

For the study, the researchers analyzed pregnant women using cannabis and found that the use of cannabis among pregnant women doubled from 3.5% to 7% in 2017 and 2002, respectively, with the highest use reported during the first trimester. About 4% of breastfeeding women were currently using cannabis.

Cannabinoids initially boost prolactin secretion through CB1R activation in the brain's pituitary gland, but later reduce levels via dopamine release. While rat studies show THC decreasing prolactin levels post-lactation, human research remains conflicting, with some suggesting reduced milk production and shorter breastfeeding in regular cannabis users. Endocannabinoids may prolong the time between suckling and oxytocin release, hindering milk ejection during breastfeeding.

The study concluded that cannabis use leads to the presence of cannabinoids in human milk, which may contribute to their long-term accumulation and inhibit milk production. Its use may also alter breast milk composition through its effects on lipid metabolism. However, substantial research is needed utilizing rigorous methods for milk collection and production to demonstrate any of these potential effects.

Reference: Castro-Navarre, I., Williams, J. E., Holdsworth, E. A., et al. (2024). Maternal cannabis use during lactation and potential effects on human milk composition and production: a narrative review. Advances in Nutrition. doi:10.1016/j.advnut.2024.100196.