By Marilyn Elias
USA Today

CHICAGO — Secondhand smoke not only can irritate your lungs, it also apparently can blacken your mood as well, a large study reports today.

Non-smokers exposed to cigarette smoke at home or work are more than twice as likely as those not exposed to have major depression, according to a report at the American Psychosomatic Society meeting in Chicago.

It’s believed to be the first U.S. study tying secondhand smoke to depression; another in Japan came up with a similar conclusion.

Unlike the Japanese research, this study confirmed exposure to smoke by measuring cotinine, a chemical that occurs in blood after breathing in smoke. There were cotinine levels for more than 3,000 non-smoking adults in a federal health study. An additional 92,000 non-smokers only reported if they lived with or worked around smokers. Everyone also filled out questionnaires on symptoms of depression.

Whether secondhand smoke was verified by the blood, those exposed to smoke were far more likely to have symptoms of serious depression, said study leader Frank Bandiera, a public health researcher at the University of Miami School of Medicine. Even working where smoking was allowed in public places more than doubled the risk of depression, he said.

There’s strong evidence that smokers have higher rates of depression than non-smokers, but studies conflict on whether the smoking came first or vice versa, Bandiera said. Animal and human studies do show that smokers have more dopamine in their brains, which he said has been tied to anxiety and depression. So secondhand smoke might have the same effect on non-smokers.

Secondhand smoke also has been found to raise the risk for heart disease and lung cancer. Another new study not reported at the meeting found that inhaling other people’s cigarette smoke could increase the risk of memory problems and dementia after age 50, say researchers at the University of Cambridge. Their research was published last month in the “British Medical Journal.”

About four out of 10 U.S. adults are covered by state or local laws against smoking in bars, restaurants and workplaces; 7 out of 10 are protected in at least one of these arenas, said Patrick Reynolds, president of the Foundation for a Tobaccofree Earth, an advocacy group.

Concern about health effects is accelerating, he adds. “There’s been a tidal wave of state laws against smoking in bars and restaurants just in the last six years.”

Twenty-four states don’t allow such smoking; 22 have passed their laws since 2003, he said.

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