Anti-tobacco initiatives have helped reduce the number of deaths from road traffic accidents in California, the World Conference on Tobacco or Health has been told.
Dr Bruce Leistikow, of the University of California at Davis, said a significant reduction in death rates from motor accidents had continued ever since the first anti-tobacco measures were taken in 1988 in the largest state in the US.
He also put forward evidence that smoking could increase violent behaviour and suicide.
Dr Leistikow told the conference that many smokers preferred cigarettes to food.
Smoking consumed 17 per cent of family income in some parts of the world. It was linked with early onset of heart disease, lung cancer and non-lung cancers.
"Lung cancers alone cause 10 per cent of new US widowhoods. Smoking is linked to the loss of a grandparent in 25 per cent of cases," Dr Leistikow said.
In a study of the effects of smoking cessation and surgery, Dr Ann Moller, a consultant anaesthetist at the Herber University Hospital in Copenhagen, Denmark, looked at 166 smokers who were waiting at least eight weeks for either hip or knee surgery.
She and her colleagues divided the participants into two groups, one of whom received intensive smoking cessation counselling and an offer of free nicotine replacement therapy.
When reassessed after surgery, the group of people who were encouraged to give up smoking before joint replacement had significantly fewer complications from the surgical procedure. In particular, the incidence of wound-related complication was much reduced in these patients. They also spent less time in the intensive care unit post-operatively.
"This study shows that we can prevent wound complication in particular by offering smoking cessation interventions prior to surgery," Dr Moller said.
"Patients found that impending surgery was a motivating factor to give up cigarettes, and they also appreciated the offer of free nicotine replacement therapy." She called for GPs to offer smoking cessation to people at the time of referral to hospital for elective surgery.
Prof Andy Parrott, of the University of East London, gave a paper which challenged the conventional thinking that smoking helps relieve stress and depression. He described research which looked at what happened when adolescents take up smoking.
"Within one year they exhibit high levels of stress and depression. And young people who become heavy smokers show higher levels of anxiety and panic attacks five years later compared to their peers who don't smoke," he said.
Emphasising that no prospective research has found that taking up smoking leads to psychological gain, Prof Parrott said all the evidence pointed in the opposite direction.
Nicotine dependency affected mood, "with normal mood while smoking being replaced by a drop in mood between smoking episodes". The worldwide costs of increased stress and depression linked to smoking could amount to billions of dollars a year.