Decision-making in teens involves a chemical called dopamine in the brain’s reward center. Dopamine helps transmit signals in the brain that make people feel happy. The number of brain receptors interacting with dopamine is higher in adolescence than at any other time of life. That means that when a teen is exposed to a reward—such as a compliment—the reward center reacts more strongly than it would for an adult. Also, being with friends increases the sensitivity to rewards and makes the already sensitive reward system even more sensitive. Feeling rewards more strongly and responding more intensely to what peers may think means that there are biological reasons for why teens sometimes decide to do things with their friends that they would never do on their own. This can be positive, by encouraging friends to take on new challenges. But it can also lead to dangerous decisions—such as drug and alcohol use.Misuse of substances like alcohol and drugs is a growing problem in the US -- and t