During the teenage years, your brain is in a critical development period. When you smoke, you can damage your brain by stunting the growth of the prefrontal corte the part of the brain in charge of “executive functions,” like choosing right from wrong. Smoking as a teen can lead to a more intense nicotine addiction because a teen brain is more susceptible to nicotine than an adult brain. It develops twice as many specialized nicotine receptors as an adult's brain. This means that you are more likely to become a lifelong smoker than somebody who first tries smoking as an adult.