Psychoactive drugs are defined as chemical substances that alter mood and behavior. The last substance I expected to see on this list was caffeine because it seems so harmless, but in reality you can become addicted to it. In high school I discovered coffee and drank a large Starbucks frappuccino every morning. When I suddenly stopped consuming them I started having pounding headaches, and I was constantly shaking. I remember staying home from school for a day when the symptoms began. Caffeine is so accessible which isn’t a bad thing, It helps a lot of people get through the day.