Smoking accounts for a quarter of all cancer deaths in the UK, and passive smoking is thought to cause hundreds more every year. But now researchers at Cincinnati Children's Hospital medical centre have found that passive smoking may also affect behaviour. The scientists studied 225 children between 5 and 11 years old, who were exposed to an average of 14 cigarettes per day. The team found that the kids exposed to the most smoke had more behavioural problems, including anxiety, depression and bad behaviour. Although the researchers studied children with asthma, they think that their results probably apply to all children - and there may be other social factors at work. Importantly, the same team previously found that passive smoking could also affect children's brain skills, including reading, maths, logic and reasoning. So maybe that's another reason to stub out the fags.