People who smoke have lower IQs than those who don't. That's according to a study of over 20,000 men carried out by Professor Mark Weiser of Tel Aviv University. The men took IQ tests and were asked about their smoking habits when they were conscripted into the Israeli army. The average IQ of the smokers was 94 compared to 101 for the non-smokers. Because the sample was so large the researchers were able to rule out the influence of socioeconomic factors and in cases where one twin smoked and the other did not the non-smoking twin was found to have a higher IQ.
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