Smoking has nothing to do with IQ

Reuters reported on October 1, 2008 on a study in the September, 2008 issue of Psychosomatic Medicine which found that smoking has nothing to do with IQ but seems more influenced by social factors such as socioeconomic circumstances. Here is a snippet from the article:

Smoking may not be the smartest habit in the world, but a person's intelligence has little to do with whether he or she begins smoking or is able to quit, Swedish researchers report.

People in lower socioeconomic levels in the Western world are more likely to be smokers, and slower to kick the habit than their wealthier counterparts, Dr. Tomas Hemmingsson and colleagues write in the medical journal Psychosomatic Medicine. Some have suggested that these individuals may be less intelligent and thus less likely to understand the risks of smoking.

To investigate, Hemmingsson and his team at the Karolinska Institute in Stockholm looked at 49,321 Swedish men born between 1949 and 1951 who had undergone IQ tests when they were 18 to 20 years old as part of conscription for military service.

At age 18, the researchers did find a relationship between lower IQ and likelihood of smoking. However, accounting for other factors known to be related to becoming a smoker, such as parental divorce, lower level of education and psychiatric diagnosis, sharply reduced the influence of IQ on smoking behavior -- although it did not eliminate it.

The researchers also found that men with lower IQs were actually at lower risk of being heavy smokers than those with higher IQ scores.

A subgroup of 694 of the men, 373 of whom smoked at age 18, were interviewed again between 1981 and 2002. At the time of follow-up, an average of 18 years later, 180 had quit. A man's IQ at 18 had no relationship with whether or not he had stopped smoking.

The study debunks the theory that people start smoking or don't quit because they have difficulty comprehending how harmful smoking is to one's health, Hemmingsson commented to Reuters Health.

In helping people to quit, he added, "the main issue would not be to explain more deeply what the health consequences are. I think most people understand the health consequences today of smoking."

Factors that are known to be associated with smoking include being a single mother and being unemployed, Hemmingsson noted. "It's other social factors that prevent people probably from stopping smoking rather than that they don't understand the health consequences of this habit."