A recent study suggests that people who smoke have lower IQs than people who don’t.
Young men who smoked a pack of cigarettes a day or more had IQ scores 7.5 points lower than non-smokers, Dr. Mark Weiser of Sheba Medical Center in Tel Hashomer and his colleagues found.
The smokers had significantly lower intelligence test scores than non-smokers, and this remained true even after the researchers accounted for socioeconomic status as measured by how many years of formal education a recruit’s father had completed.
The average IQ for non-smokers was about 101, while it was 94 for men who had started smoking before entering the military. IQ steadily dropped as the number of cigarettes smoked increased, from 98 for people who smoked one to five cigarettes daily to 90 for those who smoked more than a pack a day. IQ scores from 84 to 116 are considered to indicate average intelligence.
The study tries to spin this as “people with lower IQs are more likely to choose to smoke,” but I would expect a wider divergence if that were the case. Perhaps that is a limitation of the sample population? It wouldn’t surprise me if nicotine has a negative impact on IQ scores. What would be really telling is a study comparing IQ scores of people after they’ve quit for a few years to see if it increases.