Abstract
The main psychoactive component of cannabis, tetrahydrocannabinol (THC), is excreted into breastmilk in small quantities. The duration of detection of THC in milk has ranged from 6 days to greater than 6 weeks in various studies. Computer modeling studies predicted a half-life in milk of 12 to 39 hours, which is consistent with a THC clearance from milk in 2.5 to 8 days. Concern has been expressed regarding the possible effects of cannabis on neurotransmitters, nervous system development and endocannabinoid-related functions.[1,2] A 1-year study found that daily or near daily use might retard the breastfed infant’s motor development, but not growth or intellectual development.[3] This and other studies[4,5] found that occasional maternal cannabis use during breastfeeding did not have any discernable effects on breastfed infants, but the studies were inadequate to rule out all long-term harm and were conducted at a time when cannabis had relatively low potency. A large registry study in Australia and New Zealand suggested that postnatal use of cannabis may increase the risk of autism spectrum disorder, with male infants affected to a greater extent than female infants. However, no information on the breastfeeding status of the mothers was presented.[6] In addition to cannabinoids, milk from mothers who use cannabis contains volatile organic compounds similar to those in tobacco smoke that are known carcinogens. Smoking may result in higher amounts of some of these chemicals than vaping or oral consumption. These chemicals can also be detected in the urine of their infants.[7] Cannabis can affect serum prolactin variably and it might decrease milk supply and the duration of lactation.[8,9] Mothers with the perception that their use of cannabis is harmful to their infants are likely to discontinue breastfeeding earlier than mothers who do not believe it is harmful.[10] One preliminary study found a decrease in secretory IgA (sIgA) levels in the milk of cannabis users.[11] Two studies found decreases in the lipid content of milk, but they had opposite findings on the effects on protein and carbohydrate content.[12,13] The clinical relevance of these changes is questionable. Cannabis seeds are reportedly used orally to increase milk production in Türkiye, but no valid scientific data exist for this use.[14] For information on cannabidiol (CBD), see the LactMed record on Cannabidiol. Because of insufficient long-term data on the outcome of infants exposed to cannabis via breastmilk, health professionals’ opinions on the acceptability of breastfeeding by cannabis-using mothers varies. In general, professional guidelines recommend that cannabis use should be avoided by nursing mothers, and nursing mothers should be informed of possible adverse effects on infant development from exposure to cannabis compounds in breastmilk. Other factors to consider are the possibility of positive urine tests in breastfed infants, which might have legal implications, and the possibility of other harmful contaminants in street drugs. In addition to possible adverse effects from cannabinoids in breastmilk, paternal cannabis use may also increase the risk of sudden infant death syndrome in breastfed infants. Cannabis should not be smoked by anyone in the vicinity of infants because the infants may be exposed by inhaling the smoke.[15–18]