The title of the article in no way reflects the outcome of the research. The study compared measured IQ to a <i>decision to smoke pot</i>. There is no control group, and the study is retrospective.<p>A reader may ask how this result could arise by something other than a cause-effect relationship? Maybe people find themselves under peer pressure to (a) smoke pot, and (b) reject the value of scholarly activities. Someone might answer that IQ is predetermined, that it doesn't have any environmental component. But that idea has been falsified in animal studies, studies that show the development of new brain cells in animals that live in stimulating environments.<p>There are any number of factors that might lead an individual to simultaneously choose to smoke pot and avoid activities that might improve his IQ -- socioeconomic, genetic, and so forth. The only way to control for these things is to design a truly scientific study that <i>tells</i> experimental subjects whether they will smoke pot, rather than <i>asking</i> whether they do. But such a study would be unethical, which is why there's no science in this field of study.<p>This study is much like thousands of studies I've read over about 35 years, and all of them suffer from the same flaw -- they aren't science. Correlation is not causation.<p>The linked study represents psychology at work -- science in name only.