Marijuana use may damage brain immune cells vital to adolescent development, study suggests

THC exposure during mouse adolescence may harm brain microglia, immune cells important for healthy brain development, and may worsen genetic vulnerability linked to schizophrenia. In a study using genetically engineered mice that model human psychiatric risk, researchers treated adolescent mice with daily THC injections or saline. After a rest period, they assessed behavior and used fluorescent staining to measure microglia number and morphology. THC increased microglial apoptosis and reduced microglia, with an extra reduction in genetically at-risk mice. The effect was especially seen in the prefrontal cortex, alongside worse social memory in the THC-exposed, genetically altered animals. The researchers emphasize translation limits from mice to humans and recommend caution about adolescent marijuana use, with future work focused on molecular mechanisms and links to schizophrenia risk.