The main psychoactive ingredient in Marijuana (Cannabis Sativa) is THC (delta-9-tetrahydrocannabinol). Its effects include an increases in pulse rate, blood pressure, and heartbeat. Eyes become bloodshot and often dry mouth and throat occurs, and a crave for sweets, often referred to as "munchies". The increase in blood pressure causes the "red eyes" (easily treated with 2 drops of "Visine"), and the sudden drop of sugar level in the blood causes the "munchies" (chocolate or ice cream will increase the sugar level in the blood and the munchies will go away...)