LOS ANGELES— A tobacco company paid for a new study on teens and smoking— and results show smoking alters the way teens think.

Smoking cigarettes can alter the way a teenager's brain develops. The study from UCLA shows that the more a teen smokes, the less activity they have in the prefrontal cortex— the part of the brain that guides decision-making skills.

Researchers compared brain scans of 25 teen smokers and 25 teen non-smokers. The activity in the prefrontal cortex of smokers was lower.

A majority of smokers picked up the habit as teenagers.