The weed debate has gone on for years, but now a Duke University study of New Zealand teenagers shows that smoking marijuana regularly as a young teen will actually cost you IQ points. Researchers compared their IQ scores at age 13 and again at 38 and found that regular pot smokers had an ID drop averaging 8 points. That's more than a big deal. "An IQ is important for all aspects of life, it predicts how you do educationally, it predicts how you do in the job market. It also predicts how you end up health wise," said Dr. Richie Poulton. The study did not show the same IQ dip for those who started smoking weed after age 18. That tells researchers all they need to know about young people, that their brains are still developing. "The adolescent brain is particularly sensitive to the negative effects of substances like cannabis," Dr. Poulton added. Previous studies have suggested that smoking marijuana could damage memory and intelligence, but this is the first study that followed the same group for a long period of time. 30 years. And also controlled other factors that could alter intelligence. "We controlled for the amount of alcohol used over the same years. We also controlled for or adjusted hard drug use," Dr. Poulton said. The news is worse for people who admitted dependence on marijuana. They showed the greatest decrease in IQ scores.