What's the connection between addiction and the brain?

Our brains want us to keep doing things that we need or enjoy—like eating tasty food. That's why you sometimes eat more dessert than you know you should. That's why a little child often shouts "again!" when you do something to make them laugh.

Drugs that people use or misuse excite the parts of the brain that make you feel good. But after you take a drug for a while, your brain gets used to it. Then you need to take more of the drug to get the same good feeling. Soon, your brain and body must have the drug to just feel normal. You feel sick and awful without the drug.

NEXT: What makes someone more likely to get addicted to drugs?