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NEW YORK (Reuters Health) - Breathing secondhand smoke could increase a child's risk of mental and behavioral disorders, including attention-deficit/hyperactivity disorder (ADHD), suggests a new study.
The study adds to evidence suggesting that kids of mothers who smoked while pregnant may be more likely to have behavioral problems. Secondhand smoke exposure has also been linked to heart and breathing problems in kids.
"It's time for us to begin to prevent children's exposure to (secondhand smoke) if we are serious about preventing these diseases," Dr. Bruce Lanphear, who heads the Cincinnati Children's Environmental Health Center, told Reuters Health.
"We have sufficient evidence to prevent many of these diseases, but we don't," added Lanphear, who was not involved in the study.
The authors, led by Frank Bandiera of the University of Miami Miller School of Medicine, studied the link between secondhand smoke and mental health in a nationally representative sample of almost 3,000 kids ages 8 to 15.
Researchers measured the level of cotinine - which forms when nicotine in tobacco breaks down - in each kid's blood to find which kids had been exposed to secondhand smoke. Kids with the highest levels of cotinine were considered to be smokers themselves, and were not included in the study.
The researchers also interviewed all kids to see which ones showed symptoms of a mental or behavioral disorder.
After taking into account factors such as age and race, boys who were exposed to secondhand smoke were more likely to show symptoms of ADHD, depression, anxiety, and conduct disorder than those with no secondhand smoke exposure. Girls who were exposed to secondhand smoke had more symptoms of ADHD and anxiety only.
However, the number of kids actually diagnosed with most of the conditions was still small. While 201 kids, or about 7 percent, had enough symptoms of ADHD to be diagnosed with the disorder, only 15 kids were diagnosed with depression and 9 with an anxiety disorder.
Researchers acknowledge that it can be difficult to separate the effects of secondhand smoke from harm caused by mothers smoking while those children were in the womb.
In a commentary accompanying the study, Dr. Jonathan Samet from the Keck School of Medicine of the University of Southern California said that more research is needed to determine how exactly exposure to secondhand smoke could affect kids' brains.
Bandiera also noted that the study can't prove that secondhand smoke causes mental and behavioral disorders. But in the meantime, he told Reuters Health, "We should keep the kids away from secondhand smoke."
His study was published online Monday in the Archives of Pediatrics & Adolescent Medicine alongside research from UK authors also showing a link between secondhand smoke exposure and poor mental health in about 900 kids.
The U.S. Surgeon General has estimated that about 60 percent of children are exposed to secondhand smoke.
Lanphear said that while there might not be enough definitive evidence to tie secondhand smoke exposure to mental health problems, it would be a "surprise" if there was not a link between the two.
The authors conclude that more efforts are needed both to ban smoking in all public places where there are children and to prevent kids from being exposed to secondhand smoke at home.
SOURCE: bit.ly/ejjQQ4 Archives of Pediatrics & Adolescent Medicine, online April 4, 2011.