Every drug is different, but generally, drugs change the way your nervous system works. Sometimes, they change how your muscles function. That's why people feel different when they�re doing drugs. Their brains, nerves and muscles have been juggled around, making them have sensations they aren't used to.

Besides making you feel different and messing around with your nerves and brain, almost all drugs can make it harder to sleep. Some cause major weight gain or unhealthy weight loss. Your eyes get glassy and bloodshot. Your heart races. Sometimes you get diarrhea. Some drugs, like glue or butane, can cause immediate death. Cocaine, ecstasy and meth can give even healthy people a heart attack on the spot.

And then there are your looks. Most drugs make your hair and skin less healthy. Many make you break out -- not just on your face, but on your body. Smoking weed can make your teeth yellow, kind of like cigarettes. And, they can actually make your sex life worse because they mess with how your body responds sexually. All good reasons to avoid drugs.