ananyo writes "Back in August last year, we discussed a study reportedly showing heavy mairjuana use in teenagers had been linked to a decline in IQ in later life. Now, a new analysis suggests that the study may have been flawed. Using the same data, the researchers found that they could explain the IQ drop by properly accounting for socioeconomic factors — such as individuals from poorer backgrounds being more likely to smoke cannabis as well as having reduced access to schooling."