Although President Obama recently stated that marijuana was no more harmful than alcohol, scientific studies contradict him. A study published last month reported that teens who smoked marijuana had abnormal changes in their brain. A new study, published on January 27 in the EMBO Journal by an international team of researchers reported that marijuana use during pregnancy could cause permanent neurobehavioral and cognitive impairments by disrupting brain wiring.
The investigators examined marijuana's effects on mice and brain tissue from human fetuses; they and found that the active ingredient in marijuana, Δ9‐tetrahydrocannabinol (THC), interferes with the formation of connections between nerve cells in the cerebral cortex, the part of the brain that is responsible for higher thinking skills and forming memories. Thus, they warned that pregnant women should avoid any exposure to marijuana. They noted that the effects of prenatal marijuana exposure could persist into adulthood. The drug could have direct effects, or it could sensitize the brain to future drug exposure or neuropsychiatric illnesses.
The authors note that previous long-term studies have shown that children exposed to marijuana in the womb may have an increased risk of showing cognitive effects, be prone to take illegal drugs, having attention deficit disorder, express anxiety, or suffer from depression. They note that it currently is unclear how marijuana might affect the fetal brain at a molecular level, it appears that the brain may be particularly sensitive to THC during early development, when neurons are forming critical connections. Any drug that interferes with this development could result in permanent brain damage.
The investigators studied marijuana’s effects in three ways: (1) they grew brain cells from mice in the presence of THC; (2) they injected pregnant mice with THC; and (3) they studied the brains of electively aborted human fetuses whose mothers had used marijuana during pregnancy. They identified a specific protein in nerve cells, known as Superior Cervical Ganglion 10 (SCG10), which is crucial for normal brain wiring. Compared to individuals who were not exposed to THC, the researchers found lower levels of this protein in the brains of both human and mouse fetuses exposed to THC; this finding suggested that marijuana exposure has a specific effect on the developing brain.
The study authors note that an increasing number of women of childbearing age are using marijuana; thus, these women should be made aware of the potential impact on the brain development of their offspring. They also note that that pregnant women should avoid using marijuana for medical purposes.
The researchers are affiliated with Karolinska Institutet (Stockholm, Sweden), Icahn School of Medicine at Mount Sinai (New York, NY), University of Vienna (Vienna, Austria), School of Chemistry University of St. Andrews (St Andrews, UK), University Hospital Schleswig‐Holstein (Kiel, Germany), and Virtanen Institute University of Eastern Finland (Kuopio, Finland).