Pregnant women exposed to second-hand smoke are more likely than their unexposed counterparts to have children with psychological problems such as conduct disorder, attention deficits, and behaviour problems, a study suggests.
While such problems are known to be more common among children whose mothers smoked while pregnant, this study is the first to find that passive smoking poses a risk as well, Drs. Lisa M. Gatzke-Kopp and Theodore P. Beauchaine of the University of Washington in Seattle note in the journal Child Psychiatry and Human Development.
The findings should not "panic people who may have been exposed eating in a restaurant or doing things on a limited basis where there might be smoke," Gatzke-Kopp told Reuters Health. Nevertheless, she added, the findings underscore the risks of chronic foetal exposure to other people's cigarette smoke, which may affect psychological as well as physical health. "There is lots of evidence that heavy second-hand exposure...looks biologically the same as the mother smoking herself," she said.
Some researchers have suggested that the behaviour problems seen among the children of mothers who smoked during pregnancy, known collectively as externalising behaviours, are inherited, Gatzke-Kopp and Beauchaine note in their report. Mothers who keep smoking in pregnancy are also likely to have other risk factors for having a child with these behaviours, for example being poorer, having a lower IQ, and being more likely to choose "antisocial males" as partners, they add.
To separate the effects of cigarette smoke exposure from other factors, including genetics, the researchers looked at three groups of 7- to 15-year-old children, all of whom had serious psychiatric problems. Mothers of children in one group had smoked while pregnant, while mothers of kids in the second group didn't smoke but had been exposed to significant amounts of other people's cigarette smoke at home or on the job. Mothers in the third group didn't smoke and had no exposure to second-hand smoke.
Smoke makes the difference
Children of smokers, as well as of women exposed to second-hand smoke, were much more likely than the offspring of non-exposed women to have externalising behaviours, which include "acting out, getting in trouble, being aggressive, breaking rules," Gatzke-Kopp noted.
Scientists believe such behaviours are controlled by the brain's dopamine system, which has been shown in animal studies to be damaged by foetal smoke exposure.
"Evidence suggests that the dopamine system in the brain gets over stimulated during pregnancy," Beauchaine noted in a statement. "As a consequence, children who were exposed to smoke in utero have colic and are hard to soothe as infants. As toddlers they are overactive and oppositional. Later on they are irritable, inattentive and low on pleasure."
SOURCE: Child Psychiatry and Human Development 2007. – (ReutersHealth)
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