If anything, a ban may prompt smokers to smoke less at home, the research suggests.

The researchers base their findings on two waves of the International Tobacco Control Policy Evaluation Project (ITC Project) Europe Surveys.

These were carried out before and after legislation banning smoking in public places had come into force in Ireland, France, Germany and the Netherlands, and in the UK, excluding Scotland, before legislation was enacted.

The surveys, which were conducted between 2003/4 and 2008/9, depending on when bans took effect, involved 4634 smokers in the four countries with smoke free legislation and 1080 smokers in the UK, which served as comparison country at a time when no public/workplace smoking ban had come into force.

Before a ban came into force, most smokers had at least partial restrictions on smoking at home, although the proportions varied significantly among all four countries, with the highest levels of restrictions in Germany and France.

The presence of a young child in the household and supporting a smoking ban in bars were key factors associated with choosing to restrict smoking at home.

After legislation was enacted, the percentage of smokers who banned smoking at home increased significantly in all countries, rising by 25 percent in Ireland, 17 percent in France, 38 percent in Germany and 28 percent in the Netherlands by the time of the second survey.

This increase was irrespective of whether the public/workplace smoking ban was comprehensive or allowed for some exceptions.

Home smoking bans were more likely to be adopted when the smoker planned to quit smoking, when there was a birth of a child, and among those smokers who supported a smoking ban in bars.

In the UK, the percentage of smokers who implemented a home smoking ban also rose 22 percent between the two surveys, the second of which was carried out just a few months before the smoking ban came into force.

After taking account of several demographic and smoking history variables, the percentage of continuing smokers banning smoking at home increased significantly in all four countries, but did not significantly increase in the UK.

Current thinking suggests that the consequences of banning smoking in public end up either boosting the amount of smoking at home as smokers try to compensate—the displacement hypothesis—or encouraging smokers to apply the same restrictions at home—the social diffusion hypothesis.

“Opponents of workplace or public smoking bans have argued that smoke-free policies—albeit intended to protect non-smokers from tobacco smoke—could lead to displacement of smoking into the home and hence even increase the second hand smoke exposure of non-smoking family members and, most importantly, children,” wrote the authors.

In fact, the findings support the “social diffusion hypothesis”—that banning smoking in public places “may stimulate smokers to establish total smoking bans in their homes.”