Chiaki Itami, Jui-Yen Huang, Miwako Yamasaki, Masahiko Watanabe, Hui-Chen Lu and Fumitaka Kimura. Developmental Switch in Spike Timing-Dependent Plasticity and Cannabinoid-Dependent Reorganization of the Thalamocortical Projection in the Barrel Cortex. Journal of Neuroscience 2016:36(26);7039-7054.
A group of researchers from Baylor (Texas, USA) and Osaka (Japan) Universities showed that marijuana can adversely affect the normal development of a growing brain. These scientists proved that a chemical similar to the active substances in marijuana (cannabinoids) played an important role in the formation of nerve circuits in the brain, and that use of cannabis damaged the nerve circuits. This research looked at nerve connections from a specific area of the brain (thalamocortical area). Normally, as the brain growths in childhood, unnecessary nerve connects are “pruned” (cut) and correct connections are formed between different areas within the brain. This work was done in mice. The animals that were given cannabinoids, including the main active ingredient in marijuana, delta-9-THC, did not form correct nerve connections compared to controls (animals not treated with cannabinoids).
In summary, a study in mice showed that cannabinoids interfered with the normal growth and development of nerve connections within a specific area of the brain. It appears that the main theoretical concern would be exposure to a developing human fetus when a mother uses marijuana products. The press release from the university and Journal of Neuroscience included the caption “Adverse effects of cannabis scientifically verified, a world first.”