Cannabis and Breastfeeding: What Does the Evidence Say?

It’s funny how questions come in waves. In the past week alone, three different people have asked me about cannabis use while breastfeeding.

A doula friend texted me on behalf of a client: “Do you know of any research about edibles and breastfeeding?” Then, one of my own clients shared that she was struggling with postpartum anxiety and wondered if cannabis might help. Finally, over dinner one night, my partner casually asked, “What about second-hand cannabis smoke? Could that affect a baby?”

These questions are important. Cannabis is increasingly being legalized and is the most commonly used illicit drug during pregnancy. It is often used by women/ pregnant people to manage symptoms of morning sickness during pregnancy, and postpartum stress and anxiety (Badowski and Smith 2020). 

In Canada (where I lived) self-report rates of cannabis usage during pregnancy are 2%-5%(although these numbers are likely to be an underestimate; Badowski and Smith 2020). Given this arguably prevalent usage, we need to understand how consuming cannabis might impact our baby’s growth and development. 

When the universe hands you the same question three times, it’s probably time to head to the data.

A Frustrating Search for Answers

The first thing you notice when you start digging into the research on cannabis and breastfeeding is how much we don’t know. The majority of the studies we have are over 15 years old—ancient history in medical research terms—and most focus on smoking cannabis, not on edibles, concentrates, or other modern methods of consumption (Ordean and Kim 2020).

Why is the data so limited? That’s where things get tricky. Researchers can’t ethically run randomized controlled trials (RCTs) on breastfeeding people and cannabis. It’s a controlled substance, and offering it to parents nursing infants raises all kinds of ethical red flags. Without RCTs, we’re left with observational studies.

Observational data has its challenges. It relies on people self-reporting their cannabis use, which means we don’t always get reliable details about how much they’re using or how they’re consuming it. And there’s another complicating factor: people who use cannabis while breastfeeding are statistically more likely to use other substances like alcohol or tobacco (Badowski and Smith 2020). That makes it harder to untangle the specific effects of cannabis from everything else.

What We Do Know

Even with all these limitations, some evidence has started to emerge about cannabis use during breastfeeding. Here are a few key findings (note: this isn’t an exhaustive list, just some key points to get you started):

1. Breast Milk Composition: A recent 2023 study found that cannabis use changes the composition of breast milk (Josan et al. 2023). Specifically, it decreases immunoglobulins (important for infant immunity) and increases lactose, which could impact digestion and immune function.

2. THC in Breast Milk: THC, the psychoactive compound in cannabis, does transfer into breast milk. It’s detectable for up to six days after the last reported use (Bertrand et al. 2018; Holdsworth et al. 2024).

3. Infant Exposure: Researchers have even found metabolites of cannabinoids in the feces of breastfed infants, confirming that these compounds are passed through breast milk (Bertrand et al. 2018).

4. Second-Hand Smoke and Impairment: A 2020 study raised concerns about second-hand smoke and caregiver impairment, but it didn’t draw clear conclusions (Badowski and Smith 2020).

The overall picture? It’s murky at best.

These findings are frustrating because they don’t tell us the full story. The studies don’t address how different methods of cannabis consumption—smoking versus edibles versus concentrates—might affect infants. They don’t consider variations in THC concentration across products. And they often fail to separate the effects of cannabis from other factors, like alcohol or tobacco use.

So, where does that leave us?

Weighing the Risks and Benefits

If you’re considering cannabis use while breastfeeding, it’s important to know what we do and don’t know. We know that THC and other cannabinoids can pass into breast milk and that cannabis use may alter breast milk composition in ways (Bertrand et al. 2018; Holdsworth et al. 2024) that could affect your baby’s digestion and immune system. We know that infants breastfed by cannabis-using parents are exposed to these compounds (Bertrand et al. 2018). What we don’t know is how significant those exposures are, or what the long-term effects might be (although researchers are working on this) (De Genna, Willford, and Richardson 2022).

Some research suggests caution when using cannabis while breastfeeding (De Genna, Willford, and Richardson 2022). Other researchers highlight that such recommendations may lead people to choose not to breastfeed, increasing health disparities in populations with greater rates of cannabis use (see Iobst and Skelton 2024). Ultimately, it comes down to weighing the risks and benefits of cannabis use while breastfeeding, and how they play out in your own life. Your healthcare provider may be able to help you with this. 

We don’t have good-quality, up-to-date evidence about the impact of cannabis use during breastfeeding. Outdated methods, self-reported data, and confounding factors limit the studies that do exist. But what we do know suggests that cannabis use may have effects on breast milk composition and infant exposure to THC.

This isn’t the clear, evidence-based answer I wish I could give you—but sometimes, the research world is like that. When the evidence is murky, your best bet is to gather what information you can, weigh the potential risks, and make the decision that feels right for you and your family.

TL;DR: Cannabis and Breastfeeding

1. THC passes into breast milk and remains detectable for up to six days after use.

2. Cannabis use may alter breast milk composition, potentially affecting infant immunity and digestion.

3. Research on cannabis and breastfeeding is limited, outdated, and complicated by confounding factors.

4. While the evidence is unclear, it suggests proceeding with caution and consulting a trusted healthcare provider.

References:

Badowski Sophia, and Graeme Smith, 2020. “Cannabis use during pregnancy and postpartum.” Canadian Family Physician 66 (2): 98-103.

Bertrand, Kerri A. Nathan J. Hanan, Gordon Honerkamp-Smith, Brookie M. Best, and Christina D. Chambers. 2018. “Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk.” Pediatrics 142 (3): e20181076. https://doi.org/10.1542/peds.2018-1076

De Genna, Natacha M., Jennifer A. Willford, and Gale A. Richardson. 2022. “Long-term effects of prenatal cannabis exposure: Pathways to adolescent and adult outcomes.” Pharmacology Biochemistry and Behavior 214: 173358. https://doi.org/10.1016/j.pbb.2022.173358 

Holdsworth, Elizabeth A. Anna Berim, David R. Gang, Janet E. Williams, Caroline B. Smith, Beatrice Caffé, Olivia Brooks, Celestina Barbosa-Leiker, Mark A, McGuire, Michelle K. McGuire, and Courtney L. Meehan. 2024. “Human Milk Cannabinoid Concentrations and Associations with Maternal Factors: The Lactation and Cannabis (LAC) Study.” Breastfeeding Medicine 19 (7) 515-524.

Iobst, Stacey E., and Kara R. Skelton. 2024. “Reconsidering Breastfeeding Recommendations in the Context of Cannabis Use to Support Health Equity.” Journal of Obstetric, Gynecologic, and Neonatal Nursing 53 (5): 452-458. 10.1016/j.jogn.2024.07.002 

Josan, Chitmandeep, Samantha Shiplo, Gerhard Fusch, Sandeep Raha, and Alison K. Shea. 2023. “Cannabis use during lactation may alter the composition of human breast milk.” Pediatric Research 93: 1959-1968.

Ordean, Alice, and Gloria Kim. 2020. “Cannabis Use During Lactation: Literature Review and Clinical Recommendations.” Journal of Obstetrics and Gynaecology Canada 42 (10): 1248-1253. doi: 10.1016/j.jogc.2019.11.003