The United States has seen an increase in the amount of teenagers and young adults that smoke marijuana. The main reason for this increase is that most people believe that it is not harmful to the human body. Scientists performed a study in which they selected more than 5,000 people from the ages 18 to 30 that smoked marijuana and made these 5,000 people follow up with them at certain points over the next twenty-five years. During these follow ups, scientists tested the cognitive function through standardized tests of verbal memory, processing speed, and executive function. Scientists still had more than 3,400 people that started this study at the end of the twenty-five year period. They found that marijuana use is associated with a decrease
