Cannabis Use During Breastfeeding Can Delay Child’s Development

According to a review article in the Journal of Toxicology, the use of cannabis during breastfeeding may cause a delay in children’s motor development.

The authors of the this article found evidence that THC, the main psychoactive chemical in cannabis, could be secreted in human breast milk.

“In one feeding, the infant would ingest 0.8% of the weight-adjusted maternal intake of one joint,” as the researchers explain.

Marijuana Plant

Cannabis is the most commonly used illegal drug in the United States

Unfortunately, there has been little research concerning the effects of cannabis use during breastfeeding.

The researchers reviewed two studies which examined the effects of cannabis use during lactation and noted that, “in the first study, no significant differences were found in terms of weaning, growth, and mental or motor development with regard to age.”

On the other hand, “the second study found that cannabis exposure via the mother’s milk during the first month postpartum appeared to be associated with a decrease in infant motor development at one year of age.”

Although there needs to be more research conducted in this area before any definite conclusions can be drawn, because of the potential risks the authors of this review article strongly advise breastfeeding women to abstain from the use of cannabis.


Aurélia Garry, Virginie Rigourd, Ammar Amirouche, Valérie Fauroux, Sylvie Aubry, & Raphaël Serreau. (2009). Cannabis and Breastfeeding. Journal of Toxicology, Vol 2009. Full text:


  1. I have read extensive studies regarding the effects of Cannabis on pregnancy and breastfeeding. The international studies give very different results from the US based studies.

    There’s one factor which makes it very obvious that the validity of these studies must be questioned. In all of the dozens of studies I read there was always 5%-10% of the infants who had Fetal Alcohol Syndrome. A higher percentage of mothers tested positive for tobacco usage as well. In several studies there were a number of infants who tested positive for cocaine at birth. Because there was such a high number of infants who had been exposed to extremely high amounts of drugs and alcohol all from mothers who participated in these studies and claimed multiple times that they were only consuming Cannabis and not even over the counter aspirin during pregnancy, I’d have to conclude that there has not been any accurate studies done to date.

    In order to conduct an accurate study participants would need to submit to a full panel drug test that would show positive for THC and negative for all other substances. The other factor is the reluctance for main stream, reasonably healthy mothers to participate in studies in countries where Cannabis is not legal. Jamaica had the largest amount of completed studies because of the cultural acceptance due to the religious beliefs. Yet even though they had a larger amount of subjects to study there was still a high number of participants who showed use of other substances that contaminated the results of the study.

  2. This is a bogus review. It is not objective and misrepresents the UW study. The original study was not nearly as strongly worded because of the very minor differences (not really statistically diff).