Mother breastfeeding baby

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PULLMAN, Wash. – Could breastfeeding mothers who use marijuana be unknowingly exposing their babies to THC? A new study finds that it’s very possible. Tetrahydrocannabinol, the psychoactive component of cannabis commonly known simply as THC, has been detected in the breast milk of women who use cannabis. The findings are concerning because the study authors admit that there’s simply not much research on the effects of drugs like this on infants.

While the amount of THC discovered was low, researchers from Washington State University note that the THC concentrations found in breast milk had no consistency when it came to reaching its peak levels and eventual decline. Simply put, there was no way to tell when the impact of using cannabis would wear off and when THC levels would drop off in a woman’s breast milk. Even after 12 hours, THC continued to be detectable and would peak and drop at various times.

Cannabis has become an increasingly popular drug as more states legalize its use recreationally. Among mothers who tested positive for THC in their breast milk, their infants ingested an average of 0.07 milligrams of THC per day, according to the study published in the journal Breastfeeding Medicine. To put that into perspective, a low-dose edible contains about two milligrams of THC. While researchers believe THC exposure is likely to have negative health effects on infants, there is still no definitive proof.

“Breastfeeding parents need to be aware that if they use cannabis, their infants are likely consuming cannabinoids via the milk they produce, and we do not know whether this has any effect on the developing infant,” says Courtney Meehan, a Washington State University biological anthropologist and the study’s corresponding author, in a media release.

In the current study, the researchers analyzed the milk of 20 breastfeeding mothers who reported using cannabis. Each volunteer had an infant who was under six months-old and provided a detailed report of their regular cannabis use. The breast milk was collected after abstaining from cannabis for at least 12 hours and then at regular intervals after using the drug. Women used cannabis products of their own choosing and that they purchased themselves. The authors found that cannabis tends to linger in breast milk, even after a mother abstained from using the drug for 12 hours.

“Human milk has compounds called lipids, and cannabinoids are lipophilic, meaning they dissolve in those lipids. This may mean that cannabinoids like THC tend to accumulate in milk—and potentially in infants who drink it,” explains Meehan.

Mother breastfeeding baby
Even after 12 hours, THC in breast milk continued to be detectable and would peak and drop at various times. (© –

Frustratingly, the team could not nail down when THC concentrations peak in a cannabis user’s milk. Mothers who used cannabis only one time during the study saw their levels peak approximately 30 minutes to 2.5 hours after using cannabis. Those who used the drug multiple times during the study showed a continual increase in concentrations throughout the day.

“There was such a range. If you’re trying to avoid breastfeeding when the concentration of THC peaks, you’re not going to know when THC is at its peak in the milk,” says Elizabeth Holdsworth, a past post-doctoral researcher at Washington State University.

A separate study from the research team found breastfeeding moms mainly used cannabis to manage anxiety, chronic pain, or another mental health issues. In that report, mothers said they felt cannabis was a safer option than other medications.

“Our results suggest that mothers who use cannabis are being thoughtful in their decisions,” says Shelley McGuire, a professor at the University of Idaho. “These women were mindful about their choices. This is far from a random lifestyle choice.”

There is currently no strong evidence to support whether cannabis is a safer or more harmful alternative than conventional treatments for a variety of conditions. Meanwhile, the WSU team says more research is necessary on how all of these substances affect the health of a woman’s children. Typically, studies avoid recruiting breastfeeding women.

So far, recent research on alcohol has helped to establish guidelines for new mothers to wait at least two hours to breastfeed after drinking. With more research, the team is hopeful to establish a similar guideline for cannabis as the drug continues to soar in popularity.

About Jocelyn Solis-Moreira

Jocelyn is a New York-based science journalist whose work has appeared in Discover Magazine, Health, and Live Science, among other publications. She holds a Master's of Science in Psychology with a concentration in behavioral neuroscience and a Bachelor's of Science in integrative neuroscience from Binghamton University. Jocelyn has reported on several medical and science topics ranging from coronavirus news to the latest findings in women's health.

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