THC carried through breastmilk, researchers say, preaching caution for nursing mothers

As the use of medical cannabis continues to grow in Australia, findings from researchers at Washington State University (WSU) into breastfeeding mothers who use cannabis may be of interest to those working in early childhood education and care (ECEC) and aligned fields. 

 

The researchers found that the psychoactive component of cannabis – THC – showed up in the milk produced by breastfeeding mothers who consumed it, and that unlike alcohol, when THC was detected in milk there was no consistent time when its concentration peaked and started to decline.

 

This may mean that the children of breastfeeding mothers who use cannabis, either as prescribed or recreationally, may be affected by THC whilst in the care of ECEC settings. 

 

Importantly, little research has been conducted as to the effects and impacts of THC in breastmilk on the developing brain of a nursing infant. 

 

“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,” corresponding author Courtney Meehan said.

 

Since other research has shown that cannabis is one of the most widely used drugs during breastfeeding, the researchers aimed to uncover how long cannabinoids, like THC, persisted in breastmilk.

 

To reach their findings researchers analysed milk donated by 20 breastfeeding mothers who used cannabis. The participants, who all had infants younger than six months, provided detailed reports on their cannabis use. They collected milk after abstaining from using cannabis for at least 12 hours and then at regular intervals after use. All of this was done in their own homes, at a time of their choosing and with cannabis they purchased themselves.

 

The researchers then analysed the milk for cannabinoids. They found that the milk produced by these women always had detectable amounts of THC, even when the mothers had abstained 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,” Ms Meehan explained.

 

The research also revealed that people had different peak THC concentrations in their milk. For participants who used cannabis only one time during the study, cannabinoids peaked approximately 30 minutes to 2.5 hours after use and then started to decline. For participants who used multiple times during the study, the majority showed a continual increase in concentrations across 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,” lead author Elizabeth Holdsworth, now at The Ohio State University, explained.

 

A related qualitative study by the research team revealed that many breastfeeding mothers are using cannabis for therapeutic purposes — to manage anxiety, other mental health issues or chronic pain. The mothers often chose cannabis over using other medications because they felt it was safer.

 

“Our results suggest that mothers who use cannabis are being thoughtful in their decisions,” co-author Shelley McGuire, a University of Idaho professor who studies maternal-infant nutrition explained. “These women were mindful about their choices. This is far from a random lifestyle choice.”

 

While in most cases, the women were using cannabis as alternative treatment for a variety of conditions, Professor McGuire pointed out that there is no evidence yet whether it is safer or more harmful.

 

In fact, she said, scientists know ‘almost nothing’ about how many commonly used drugs may impact breastfeeding babies, partly because women, especially those who are breastfeeding, have historically been left out of clinical trials on medicines.

 

“This is an area that needs substantial, rigorous research for moms to know what’s best,” she urged.

 

Access the findings in full here.