Sure. I'm more than happy to respond. Thank you, Madam, for the question.
Essentially, this study was looking at over 1,000 people born in the years 1971 and 1972 in the fourth largest city in New Zealand, Dunedin. It was an extraordinary study. I don't want to say that it was unprecedented, but it's a rare study. That you can enrol every single person born in this one large city in two years in a research project that would span their lifetimes is fascinating.
Essentially, researchers check in with them every five to ten years on many different issues and levels, on all sorts of things. This time when they checked in on them.... They had looked at their cannabis use when they were younger through surveys, but they also made sure that this was consistent over time, so it was accurate.
This time, for those people who had used cannabis three to four times a week for three to four years, I believe—and I will get you the exact study to make sure the numbers are correct, as this is off the top of my head—even if those people had stopped using cannabis in early adulthood, by the time they were 38 years old, which was the last time they were checked on, about four years or so ago, it was shown that, controlling for alcohol—even alcohol did not show this—controlling for socio-economic background and for education, there was a significant risk, I believe at the 0.01 level, if you want to get specific about the regression—which is important—of basically six to eight points, depending on a few different factors, whether it was six or eight, but the bottom was six points and the top was eight points in terms of the range, shown of a reduction in IQ that could not be explained by education, parental involvement, alcohol use, and other drug use. In other words, they had controlled for this.
This was such an extraordinary finding that it was understandably challenged by some people. A researcher in Norway challenged them to go back and redo their calculations based on a different formula and using different things. They went back, redid it, and found the exact same results. These are findings that are certainly talked about in scientific spheres still, and there's certainly follow-up to do, but it confirms what we know about school dropouts, what we know about attention span, and what we know about other things related to education.