Dr. Madeline Meier, of the famous IQ and marijuana study, responds to new IQ study

A writer with Washington Post‘s online blog, Wonkblog, who has a history of pro-marijuana leaning articles, recently published a story called, “No, marijuana use doesn’t lower your IQ”

The article goes on to question the association between marijuana and IQ based on findings from the ASLPAC study just released. We asked Dr. Madeline Meier, now at ASU, who co-authored the now famous Dunedin study showing a significant reduction in IQ among heavy adolescent marijuana users, about the Wonkblog accusations. Here was her reply:

“This new paper looks interesting. It does not relate in any way to our findings from the Dunedin Study, however.

Our finding was that adults who were long-term dependent on cannabis and those who used cannabis 4 or more times per week during the 20 years after adolescence, had lost IQ points by age 38. Those who lost the most IQ points were those who had started their cannabis use youngest, as teens.

There is no reason to expect that teens who have used cannabis only 50 times would already show a loss of IQ points by age 15. The ALSPAC study would need at least 20 more years of follow up, and data on cannabis dependence, before it could be compared to the Dunedin Study.”