JAMA logoSmoking has always been considered a health damaging habit. Besides, harming the smoker, numerous studies have claimed this addiction to be harmful for others around them too. A latest investigation commenced by experts from the University College London apparently suggests that exposure to secondhand smoke may be linked with psychological distress and the risk of future psychiatric hospitalization among healthy adults.

For the study, scientists analyzed 5,560 non-smoking adults at an average age of 49.8 years and 2,595 smokers belonging to an average age group of 44.8 years. None of the participants belonging to the smokers group had a history of mental illness and all had initially participated in the Scottish Health Survey in 1998 or 2003.

The authors explained, “A growing body of literature has demonstrated the harmful physical health effects of secondhand smoke exposure. Given the highly prevalent exposure to secondhand smoke—in the United States, an estimated 60 percent of American non-smokers had biological evidence of exposure to secondhand smoke—even a low level of risk may have a major public health impact.”

All the participants were given a questionnaire to fill in details about their psychological distress. During the follow up of the study which lasted for almost six months, the investigators noted the number of times participants were admitted to psychiatric hospitals. Examining the saliva levels of cotinine the authors evaluated the exposure to secondhand smoke among non-smokers. The ultimate product is believed to be formed when nicotine is broken down in the body. These findings were put forth by Mark Hamer, Ph.D., of University College London, and colleagues.

The investigators added, “Taken together, therefore, our data are consistent with other emerging evidence to suggest a causal role of nicotine exposure in mental health. To our knowledge, this is the first study to demonstrate a prospective association between objectively assessed secondhand smoke exposure and mental health in a representative sample of a general population.”

The investigators observed that almost 14.5 percent of the participants reported psychological distress. It was revealed that non-smokers adversely exposed to secondhand smoke with cotinine levels between 0.70 and 15 micrograms per liter reported higher chances of psychological distress as compared to those with no detectable cotinine.

By the time the follow up continued around 41 individuals were admitted to psychiatric hospitals. Increase in hospitalization for depression, schizophrenia, delirium or other psychiatric conditions were monitored in both smokers and non-smokers with high exposure to secondhand smoke. But non-smokers with low levels of secondhand smoke exposure displayed lower chances of getting hospitalized.

Experiments conducted on animals suggest that tobacco seemingly results to a negative mood. Similar studies undertaken on humans reveal a possible link between smoking and depression.

The study is published online and will be available in print in the August issue of Archives of General Psychiatry, one of the JAMA/Archives journals.