Q. How do drugs affect the brain?  

A. It depends on the brain and on the way in which the drug interacts with it. Every action has a reaction. Each drug is designed to produce a reaction. Hopefully, the reaction is a helpful one; but even necessary medications tend to have some undesirable side effects. The reaction depends on what it does when it binds to receptor molecules on the surface of the cell and gets inside. Think of the drug as a key and the receptor molecule as a lock. The drug must find a lock that fits its key. Once inside, the drug triggers the cell in some way or other. It may release a brain chemical that will give you a reaction. It may make you sleepy or wake you up. It may trigger the Brain Reward System to release dopamine to make you feel better—that over time can turn into an addictive behavior. Some can trigger a mental disorder such as a psychosis, and some can eventually kill you. Just remember that when you make choices, every action has a reaction.