Friday, February 8, 2019

Mary Jane and Breast Milk, a Safe Combo?

The legalization of marijuana occurred late last year and, once the excitement has died down, there remains a lot of consideration that need to be
addressed about recreational use of marijuana and its effects on different population groups.

To begin, the safety behind marijuana is murky at best. Many studies suggest that exposure to the psychoactive component of marijuana (THC) in adolescents (who have developing brains) may lead to or uncover incidents of psychoses, and in some circumstances, uncover underlying diseases like schizophrenia. However, other studies are investigating its use as a potentially safer alternative for pain management, an attractive therapy option considering the current opioid crisis arising from opioid overuse. Amidst the sparse data that is currently present (in a soon to be or already exploding field of research), one issue that still requires more conclusive answers is the effect of THC on infants or breastfeeding mothers.

As part of my rotation at the Center for Mental Health and Addiction, marijuana came up quite frequently as a topic of discussion. What effects did it have on the baby still in the womb who were exposed? If there were no immediate effects, would there be any long-term neurodevelopmental impacts on the babies who were exposed? One case that was mentioned to me in passing involved a parent who was unsure if they can smoke cannabis as a sleeping aid, while breastfeeding their baby in the evening time.  I imagine that the patient’s clinician did not have an easy time providing an answer.

From a pharmacological perspective, it is known that breastfeeding infants will be exposed to marijuana used by the nursing parent (regardless of how the parent takes in the substance, from eating edibles to vaping). The chemicals found in marijuana like THC and CBD are considered lipophilic molecules, which means they are easily taken up by and stored in adipose tissue and cells and would most likely pass easily from the mother to the milk. Once taken up by the infant, the molecules will be stored in lipid-rich tissues like the brain. These molecules tend to stay in the body for long periods of time, and even longer if the person tends to use marijuana on a regular basis, taking at least 30 days for the chemicals to completely clear the mother’s system. A recent study done by Bertrand et al. in 20181 also found that THC, the most psychoactive component of marijuana (and thus potentially the most damaging) was measurable abundantly in breast milk for at least 6 days after marijuana use.

From a clinical perspective, historically, there used to exist little conclusive evidence that marijuana ingestion by babies through breast milk causes harm, largely due to the lack of studies done in the area. To date, there is no conclusive data that adequately addresses the effects of marijuana exposure on long-term neurodevelopment. However, there is an emerging trend of immediate and negative effects on both parents and infant associated with marijuana use during breastfeeding. A study by Astley and Little2 suggested that exposure to THC through breastmilk in the first month of life could result in decreased motor development at 1 years old. In terms of the immediate effects of marijuana exposure through breastmilk, lethargy, less frequent feeding, and shorter feeding times have been observed.3

At the same time, a mother’s breast milk is one of the most effective sources of nutrition of a growing infant, and a fed infant will fare better than an unfed infant.  Breast milk is one of the best foods for babies as it is packaged with all that a baby may need, from carbohydrates, proteins, fats, minerals, vitamins, and hormones, to maternal antibodies. Psychologically, breastfeeding facilitates bonding between mother and infant. While it would benefit the parent to err on the side of caution and cease any marijuana use until the baby grows up to no longer require breastfeeding, parents who cannot stop marijuana use may be helped through a harm reduction approach of lowering dose and frequency as much possible while continuing to breastfeed. The risks and benefits of marijuana use during breastfeeding should be provided for breastfeeding mothers to address any misconceptions about marijuana use, and close support should be offered for both parent and the developing infant.

Undoubtedly, the question of marijuana's safety in adults, in pregnant mothers and every demographic in between is something every healthcare provider needs to review. As the use of marijuana becomes more and more accepted here in Canada, more and more patients and parents will be curious about very same things, and healthcare providers will need to help them navigate through these murky waters, hopefully giving them sound, evidence-based information to make an informed decision.


  1. Bertrand KA, Hanan NJ, Honerkamp-smith G, Best BM, Chambers CD. Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk. Pediatrics. 2018;142(3)
  2. Astley S, Little RE. Maternal marijuana use during lactation and infant development at one year. Neurotoxicol Teratol 1990;12:161-8.
  3. Committee on Nutritional Status During Pregnancy and Lactation, Institute of Medicine. Illegal drugs. Washington, DC: National Academy Press; 199