June 8th, 2010
03:57 PM ET

Secondhand smoke linked to depression, other psychological distress

By Caitlin Hagan
CNN Medical Associate Producer

Researchers say exposure to secondhand smoke, even at low levels, is associated with depression and other types of psychological distress. Their study and findings are published in the Journal of the American Medical Association Archives of Psychiatry.

The university researchers from London and Edinburgh, Scotland took saliva samples from more than 8,000 participants in the Scottish General Health survey and tested them for cotinine, a metabolite of nicotine. Using those objective measurements, the study authors found a strong association between exposure to secondhand smoke psychological health issues, including depression, delirium, mood swings, and even schizophrenia. The association became stronger as the participants' cotinine levels increased.

"You need to think of secondhand smoke as a toxic stew," says Thomas J. Glynn, the Director of Cancer Science and Trends at the American Cancer Society. "There are more than 4,000 compounds in both mainstream smoke and secondhand smoke. And the list of chemicals is frightening."

The study only found an association between the two, not a cause and effect relationship. Still, the study authors hypothesized that the negative psychological effects were caused by the smoke interrupting the body's immune system or weakening various pathways in the brain, including the dopaminergic pathway responsible for transmitting dopamine.

According to the American Cancer Society, 50 to 60 percent of Americans are still exposed to secondhand smoke. The Environmental Protection Agency has classified secondhand smoke as a "known human carcinogen", meaning it's been proven to cause cancer in humans. It's responsible for various illnesses and conditions, from lung infections and asthma attacks to nearly 750,000 middle ear infections in children every year.

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soundoff (5 Responses)
  1. ERPeay

    My God, at this late date we're still taking the time to stomp on smoking? We already know that it is responsible for train crashes, ear wax and earthquakes. And what does it matter when global warming is going to do us all in, smokers and non-smokers alike?

    June 9, 2010 at 02:23 | Report abuse | Reply
  2. Heather F

    Growing up with two smoking parents in addition to a crazy childhood, explains a lot of why I've had depression since I was five years old.

    June 9, 2010 at 09:30 | Report abuse | Reply
  3. Kathy

    Another reason to get away from the smoker.

    June 9, 2010 at 10:15 | Report abuse | Reply
  4. Mike

    This article doesn't do enough to explain that a correlation does not necessarily equal causation. There is a brief mention of this, but the article prefaces the warning about interpreting statistical studies with a statement by a researcher that smoke is a toxic stew.

    It's long been shown that cigarette smokers are more likely to have psychological issues like depression, mania, or schizophrenia. However, it could be likely that people with mental health issues smoke because the nicotine high helps alleviate or ignore symptoms of mental illness.

    Here, is it *possible* that something in tobacco causes mental illness? Yes, it's possible. However, people are often exposed to significant secondhand smoke in their homes; mental illness has a strong genetic component; and therefore it could be that they're schizophrenic because their parents passed down genes for schizophrenia. Oh, and by the way, the parents smoke because it calms them down during hallucinations.

    June 9, 2010 at 14:53 | Report abuse | Reply
  5. Health News

    Obviously if you smoke, it will somehow influence your children to smoke, so either be smart when smoking, or just DON'T SMOKE ANYMORE.


    June 28, 2010 at 16:23 | Report abuse | Reply

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