Can cannabis affect breast milk?

Yes, cannabis can affect breast milk. Rhonda Patrick has discussed that breast milk samples from lactating women who used marijuana contained detectable levels of THC (tetrahydrocannabinol), the primary psychoactive component of cannabis. This was true for 63% of the samples, up to six days after the last reported use. Exposure to marijuana through breast milk in the first month of an infant's life is associated with decreased motor development at twelve months. Rhonda Patrick advises caution when using social drugs like cannabis during breastfeeding because of these potential risks to the infant 1.