Researchers from the University of Kuopio in Finland have found that sons of mothers who smoked during pregnancy were more than twice as likely to go on to commit a violent crime or repeatedly commit crimes compared with sons of women who did not smoke.

The study is published in the June issue of the AMERICAN JOURNAL OF PSYCHIATRY. The researchers collected information about 5,636 males and their mothers from the time the women were six months pregnant until the children were 28 years old.

The researchers speculate that smoking during pregnancy may affect the chemistry of the developing baby's brain.

The researchers could not examine, however, whether or not the women who smoked were also more likely to commit crimes.