Secondhand Smoke a Mental Health Hazard?

Study finds association with psychiatric woes, but experts say cause-and-effect isn't proven

MONDAY, June 7, 2010 (HealthDay News) -- Long linked to physical ailments such as asthma, heart disease and lung cancer, secondhand smoke may now be tied to an increase in mental woes, new research suggests.

Prolonged exposure to another's noxious tobacco fumes could up the odds for psychological distress, depression, schizophrenia and delirium, British researchers say.

"In the U.S., an estimated 60 percent of non-smokers have biological evidence of exposure to passive smoke. Thus, in order to improve mental and physical health, people should be made aware of these harmful effects," said lead researcher, Mark Hamer, from the Department of Epidemiology and Public Health at University College London.

"Exposure to passive smoke was associated with higher levels of psychological distress and greater risk of future psychiatric illness," he said.

The report is published in the June 7 online edition of the Archives of General Psychiatry.

For the study, Hamer's team collected data on over 5,500 non-smokers and nearly 2,600 smokers. None of these people had any history of mental illness at the start of the study, the researchers noted. In addition, the researchers measured levels of cotinine in saliva, which indicates an individual's level of exposure to tobacco smoke.

Over six years of follow-up, 14.5 percent of the individuals were found to be suffering from psychological distress. People who did not smoke, but who were exposed to high levels of secondhand smoke, were almost 50 percent more likely to suffer from psychological distress than those not exposed, the researchers found.

In addition, during the six-year follow-up period, 41 of the participants were admitted to psychiatric hospitals for problems such as depression, schizophrenia, delirium or other psychiatric problems. Those with high exposure to secondhand smoke were nearly three times as likely to be admitted versus people unexposed to the fumes, the study authors found.

Stanton A. Glantz, a professor of medicine and director of the Center for Tobacco Control Research and Education at the University of California, San Francisco, commented that "this is an important and well-done study that shows that secondhand smoke is even more dangerous than we previous thought."

Dr. Norman H. Edelman, a scientific consultant for the American Lung Association, agreed that "this is a very well done, potentially important study."

Edelman said, "It's not just that people with psychiatric symptoms tend to smoke more or be around those who smoke more, it may be that the exposure to smoke adds to their symptoms."

However, another expert questions the validity of the findings. While smoke may make one more susceptible to mental problems, people predisposed to mental health woes may find themselves in smoky environments more often.

Dr. Ted Schettler, the science director of the Science and Environmental Health Network, reasoned that, perhaps "nicotine is associated with an increased likelihood of psychological problems."

But, he added, "On the other hand, you can easily imagine that people who are in stressful life circumstances are also finding themselves in more smoke-filled environments. I don't know that you can separate it out."

More information

For more information on secondhand smoke, visit the U.S. National Library of Medicine.

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