Claims that cannabis use is associated with lower cognitive functioning are largely based upon the findings of a single longitudinal study. The paper, published by Madeline Meier and a team of Duke University researchers in 2012, reported that the onset of cannabis use in early adolescence was associated with an average decline of eight IQ points by middle-age.
However, a critique of Meier’s study, published in the Proceedings of the National Academy of Sciences, opined that the reported differences in IQ were consistent with socioeconomic differences among the study’s participants and likely were not attributable to marijuana use. (This criticism is hardly surprising as data has historically shown that those of greater economic means tend to test higher on IQ tests than those who are poorer, and critics have also raised questions as to whether the test itself may possess inherent racial biases.) It countered that the Duke