Smoking

Smoking as a child and adolescent has been proven to produce large health issues in young adults, including respiratory illnesses, a decrease in physical activity, poor lung development, as well as other things.

People who start smoking at an earlier age are more likely to develop a strong addiction to nicotine, making it very difficult for them to quit.

Tobacco use has also proven itself to be a gateway drug leading to the use of alcohol and illicit drugs.

Source: http://www.lungusa.org/site/c.dvLUK9O0E/b.39871/
k.9A62/Smoking_and_Teens_Fact_Sheet.htm