Smokers are known to suffer from high rates of depression and other mental health
problems, and now a study reports that even people exposed to
secondhand smoke are at significantly increased risk — and more likely
to be hospitalized for mental illness.

The study
analyzed data from the Scottish Health Survey of 1998 and 2003, a
periodic look at a nationally representative sample of about 5,560
nonsmoking adults and 2,595 smokers. The researchers used a 12-item
questionnaire to assess mental health, including sleep problems and
symptoms of depression and anxiety. Salivary levels of cotinine, a nicotine byproduct, were used to assess exposure to secondhand smoke.

Nonsmokers exposed to secondhand smoke were 1.5 times as likely to
suffer from symptoms of psychological distress as unexposed nonsmokers,
the study found, and the risk increases the greater their exposure to
passive smoking.

And though psychiatric hospitalizations were rare over all, the exposed
nonsmokers were also almost three times as likely to have to be
admitted to a psychiatric hospital, according to the study, published
online June 7 in Archives of General Psychiatry.

While the association between smoking and mental health problems has
long been known, researchers have never been able to establish whether
people with mental illness are more likely to pick up the cigarette
habit, or whether smoking may actually help cause mental illness, said
the paper’s lead author, Mark Hamer, a senior research fellow at
University College London.

“This research goes some way toward suggesting nicotine is having some
sort of impact on mental health,” Dr. Hamer said. “But of course, we
need to do further work.”