Passive smoking likely to cause depression

A study discovered that people exposed to high levels of second-hand smoke were 44% more likely to have damage caused to their brain - affecting things like memory and the ability to perform calculations.

Scientists had already established that smokers are at a greater risk of suffering from dementia, but the study - led by a team from Cambridge University - was the first to look at the effects of passive smoking.

The authors of the report said one reason for their findings may be that second-hand smoking leads to an increased risk of heart disease and stroke, which in turn can heighten the risk of cognitive impairment and dementia.

Nearly 5,000 non-smokers in England aged 50 and over took part in the study, and were tested to see how much cotinine - a marker of nicotine exposure - they had in their saliva.

They were then split into four equal groups, based on the levels found, before everyone underwent neuropsychological testing including verbal memory and numerical calculations.

The results, published in the British Medical Journal, showed those with the third highest level of cotinine concentration were 8% more likely to have suffered cognitive impairment than those in the lowest group.

That increased to 13% among the group with the second highest level, and to 44% in the group which had most cotinine in their saliva.

Dr David Llewellyn, who led the study, said: "Our results suggest that inhaling other people's smoke may damage the brain, impair cognitive functions such as memory, and make dementia more likely.

"Given that passive smoking is also linked to other serious health problems such as heart disease and stroke, smokers should avoid lighting up near non-smokers."

The survey found results were similar for people who had never smoked and those who had once been smok