It is difficult to study the effects of cannabis use on infants due to the reliance on self-reported data, which may not accurately capture the full details of exposure. However, in light of the potential risk of negative obstetric outcomes, the American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) discourages all forms of cannabis use during pregnancy and lactation.1,2
Cannabis exerts its effects via compounds called cannabinoids, with Delta-9 tetrahydrocannabinol (THC) being the most psychoactive.1,2 Cannabinoids primarily act on the central nervous system via cannabinoid receptor 1 (CB1) and immune system tissues via cannabinoid receptor 2 (CB2). The onset and duration of action of THC depends on the route of exposure.
There are insufficient data to evaluate the effects of cannabis exposure on infants. Studies have shown that THC can be passed on to infants through breastmilk, but there is limited information about the effect this may have on infants and their development. Similarly, there is limited information about the effect of second-hand cannabis smoke on infants. Given an absence of definitive data showing a lack of harm, ACOG and AAP discourage cannabis use.1,2
A 1990 study observed that of 136 breastfed infants, a group of 17 subjects with 15-30 days of exposure to cannabis during the first month of lactation exhibited decreased motor development on the Bayley Scales of Infant Development (BSID) compared to matched controls (difference of 12 points).3 However, this difference decreased to five points at three months. Mental development was similar regardless of prenatal or perinatal cannabis use. These findings persisted after controlling for maternal smoking, drinking, and cocaine use during pregnancy and lactation. The authors note that cannabis exposure in the first trimester may have confounded the association between cannabis exposure during lactation and infant outcomes.
A 1985 study examined the effect of cannabis use on birth as well as postnatal outcomes. Of 756 participants, 257 self-reported cannabis use.4 There was no observed associations between cannabis exposure postpartum and motor and mental skills using the Brazelton scale. At one year, there continued to be no association between development and cannabis use.
Overall, the results of studies on the effects of postnatal cannabis use are heterogenous. It is also to be acknowledged that a common limitation among these studies is inadequate data on the dosage, frequency, and route of cannabis consumption and a reliance on self-reported data and urine tests that may not accurately capture the exposure to cannabis. However, the presence of data that suggest potential harmful effects, in the absence of definitive data to show otherwise, has led to the recommendation that mothers be encouraged to discontinue all cannabis use during lactation.
However, while causality has not been definitively established, cannabis use has been linked to a number of negative outcomes, including impaired neurocognitive and psychosocial functioning, mental health problems (e.g., psychosis, schizophrenia, depression, suicidal behaviors), and respiratory conditions, reproductive, cardiovascular, gastro-intestinal conditions.5 A 2017 meta-analysis of fifteen studies found that in every study analyzed, cannabinoids and cannabinoid metabolites could be detected in the bodily fluids of those exposed to second-hand cannabis smoke.6 Two studies reported that participants experienced psychoactive effects from second-hand smoke. Additionally, there is evidence that cannabis use alters brain structure in adolescents more than in adults, indicating that younger people are more susceptible to the potential negative effects of cannabis.7
A multinational clinical practice guideline called Lower-Risk Cannabis Use Guidelines (LRCUG) advises that while there are safer ways to use cannabis relative to less safe methods and quantities, there is no universally safe level or method of cannabis use, and the only reliable way to avoid risk is to abstain from exposure.5
References
- Committee Opinion No. 722: Marijuana Use During Pregnancy and Lactation. Obstet Gynecol. Oct 2017;130(4):e205-e209. doi:10.1097/aog.0000000000002354
- Ryan SA, Ammerman SD, O'Connor ME. Marijuana Use During Pregnancy and Breastfeeding: Implications for Neonatal and Childhood Outcomes. Pediatrics. Sep 2018;142(3)doi:10.1542/peds.2018-1889
- Astley SJ, Little RE. Maternal marijuana use during lactation and infant development at one year. Neurotoxicol Teratol. Mar-Apr 1990;12(2):161-8. doi:10.1016/0892-0362(90)90129-z
- Tennes K, Avitable N, Blackard C, et al. Marijuana: prenatal and postnatal exposure in the human. NIDA Res Monogr. 1985;59:48-60.
- Fischer B, Robinson T, Bullen C, et al. Lower-Risk Cannabis Use Guidelines (LRCUG) for reducing health harms from non-medical cannabis use: A comprehensive evidence and recommendations update. Int J Drug Policy. Jan 2022;99:103381. doi:10.1016/j.drugpo.2021.103381
- Holitzki H, Dowsett LE, Spackman E, Noseworthy T, Clement F. Health effects of exposure to second- and third-hand marijuana smoke: a systematic review. CMAJ Open. Nov 24 2017;5(4):E814-e822. doi:10.9778/cmajo.20170112
- Blest-Hopley G, Giampietro V, Bhattacharyya S. Residual effects of cannabis use in adolescent and adult brains - A meta-analysis of fMRI studies. Neurosci Biobehav Rev. May 2018;88:26-41. doi:10.1016/j.neubiorev.2018.03.008
