A study came out last summer that found that blazing up regularly as a teen could make you dumber. However, new analysis of that data finds that the original research was flawed, and that the lowered IQ scores of the study’s participants may have been caused by other factors.
The original study—published in Proceedings of the National Academy of Sciences (PNAS) last August—tracked over 1000 people from Dunedin, New Zealand for 25 years. Their IQs were tested when they were 13 and again when they were 38. They were asked periodically throughout the years, about their marijuana use. Those who said they were hooked on reefer by the age of 18 showed a drop in IQ points, leading researchers at Duke University to suggest that weed is harmful to the adolescent brain.