PASSIVE smoking has been linked to mental health problems for the first time by a scientific study that suggests those exposed to cigarette fumes are three times more likely to be admitted to psychiatric hospital than those free from nicotine exposure.
A study of more than 8,000 Scots also found that passive smokers were more likely to report depressive moods than non-smokers who steered clear of inhaling other people's cigarette smoke.
The research was conducted by scientists at University College London, who examined a sample of 5,560 non-smoking adults and 2,595 smokers drawn from the Scottish Health Survey, a database representative of the general population.
Non-smokers were tested for second-hand smoke exposure by testing participants' saliva for cotinine –- a substance that acts as a marker that can reveal how much smoke a person has been exposed to.
Participants also filled out a questionnaire designed to measure mental health by examining happiness levels, experience of depressive and anxiety symptoms and sleep disturbance over four weeks.
The questionnaire revealed how many members of the sample had suffered "psychological distress" – an episode defined as a low mood that fell short of clinical depression but could develop into a more serious condition. Analysis of the data found that passive smokers were more likely to suffer "psychological distress" than those free from tobacco smoke.
In the non-smokers with very low levels of passive smoke exposure, the rate of psychological distress was nine per cent. Among the non-smokers who experienced high exposure, the rate was 14 per cent.
"We found quite a strong association between passive smoke exposure and poorer mental health," said Dr Mark Hamer, the head of research.
Sheila Duffy, chief executive of Ash Scotland, said:
"We have known about links between active smoking and mental health problems, but this new research suggests that second-hand smoke is even more harmful than we thought."