Teen Pot Use Kills IQ? New Study Says No Socioeconomic differences may explain earlier findings: report By Matt Cantor, Newser User Posted Jan 15, 2013 1:33 AM CST 30 comments Comments This Nov. 8, 2012 file photo shows marijuana plants flourishing under the lights at a grow house in Denver. (AP Photo/Ed Andrieski, File) (Newser) – Justin Bieber might not be as dumb as you think he is: Over the summer, word was that teen marijuana use could reduce IQ—but a new investigation rejects that initial study. Duke scientists, among others, had reviewed the IQs and pot habits of some 1,000 people in a New Zealand town between the ages of 13 and 38. They found that IQ scores sank among heavy users. But an Oslo researcher says differences in socioeconomic status could just as easily have explained the apparent IQ drop. His study used a computer simulation to test how IQ scores could shift based on socioeconomic status, including education, income, and career. Trends in his findings matched those found in the pot study. He says he's not sure his study overrules the original one, but it points to potential flaws. The Duke team analyzed his results and say they're wrong, and outside experts say the original study hasn't been disproved beyond doubt, the AP reports.