THC mimics and disrupts the brain's natural endocannabinoid system — a network of receptors that plays a critical role in regulating mood, memory, stress response, sleep, and appetite. For occasional adult users, these effects are largely temporary. But for young people whose brains are still developing, for those with underlying mental health vulnerabilities, and for heavy or long-term users of high-potency products, the disruption can be more profound and longer lasting.