Israeli study - are non-smokers smarter than smokers?

February 24, 2010 - Cigarette smokers have lower IQs than non-smokers, and the more a person smokes, the lower their IQ, a study in over 20,000 Israeli military recruits suggests.

PAPER: Cognitive test scores in male adolescent cigarette smokers compared to non-smokers: a population-based study, Mark Weiser (, Salman Zarka, Nomi Werbeloff, Efrat Kravitz & Gad Lubin, Addiction 105(2 - February 2010) 358-363, 2010 (published online: 17 Nov 2009), ABSTRACT..

To better understand the smoking-IQ relationship, the researchers looked at 20,211 18-year-old men recruited into the Israeli military. The group did not include anyone with major mental health problems, because these individuals are disqualified from military service.

According to the investigators, 28 percent of the study participants smoked at least one cigarette a day, around 3 percent said they were ex-smokers, and 68 percent had never smoked. 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.

Recruits aren't allowed to smoke while intelligence tests are administered, the researchers note, so it's possible that withdrawal symptoms might affect smokers' scores. To address this issue, they also looked at IQ scores for men who were non-smokers when they were 18 but started smoking during their military service. These men also scored lower than never-smokers (97 points, on average), "indicating that nicotine withdrawal was probably not the cause of the difference," the researchers say.

The researchers also compared IQs for 70 pairs of brothers in the group in which one brother smoked and the other did not. Again, average IQs for the non-smoking sibling were higher than for the smokers.

The findings suggest that lower IQ individuals are more likely to choose to smoke, rather than that smoking makes people less intelligent, Weiser and his team conclude.

We must remember that Nicotine has a negative impact on the developing adolescent brain..

Reference: Are non-smokers smarter than smokers?, SOURCE: Addiction, February 2010, Reuters, 2/23/2010.

Photo - MacYapper blog..