New research has indicated that smoking may lower IQ levels. A study of 20,000 young adult males found that the more heavy the smoking of a person, the lower his IQ was likely to be.
The study, conducted by the Sheba Medical Center at the Tel Hashomer Hospital in Israel, found that men who smoked a pack or more of cigarettes a day averaged an IQ seven and a half points lower than that of those did not smoke.
"IQ scores are lower in male adolescents who smoke compared to non-smokers and in brothers who smoke compared to their non-smoking brothers. The IQs of adolescents who began smoking between ages 18 to 21 are lower than those of non-smokers," said lead researcher Mark Weiser. He added that it was unclear if smoking caused lower IQ or whether intelligent people did not take up the habit.
Non-smokers had an average of 101, while smokers had an average score of 94. These differences were present in siblings as well, with the ones who smoked averaging a lower IQ than the non-smoking brother..