All drugs affect the brain. That's why they can make you feel high, low, fast, or slow. They also might make you see things that aren't there.
Some drugs can hurt your brain and affect how you act and how your body feels. These problems might last just a little while, or they may last for the rest of your life.
Some drugs can make your mood change quickly. You might get sad, angry, or scared for no reason. You might overreact to little problems. You might get violent or think that someone wants to hurt you.
Some drugs can make it hard to pay attention, remember things, or think clearly. That's why people often make bad decisions when they're on drugs.
Drug use can also hurt your ability to enjoy things. When you're addicted, things that used to make you feel good no longer make you happy. You might not enjoy seeing your friends or watching your favorite movie because all you can think about is getting more drugs. Usually, you can start enjoying things again once you stop using drugs, but it may take time.