Extensive Israeli research, that included over 20 thousand subjects, found that those who smoked a pack a day or more had a lower IQ by 7.5 points than non-smokers.
Investigator, Dr. Mark Weiser and his colleagues at the Sheba Medical Center in Tel Hashomer sought to examine the link between smoking and IQ among 20,211 boys aged 18 about to enlist in the IDF. They found that those who smoked had significantly lower IQ scores than those who do not smoke. These results remained consistent even after the researchers removed variables that could skew the results such as socioeconomic status or years of schooling.