SCIENTISTS at a conference in Edinburgh yesterday warned against placing unrealistic expectations on genetic therapy as a cure for disease at the expense of lifestyle and diet.

Young smokers, in particular, were cautioned that gene-based cures for cancer were a long way off.

Professor Elizabeth Russell, of Aberdeen University, told the conference most diseases had more than one cause: ''The genetic contribution is no more absolute or dominant than that of other causal factors.''

She said Scotland could learn from the Finnish experience where a community-based approach to lifestyle and environment had brought good results in preventing heart disease.

Cancer prevention would also benefit from a more social approach. ''Banning smoking in pubs and restaurants is actually helpful to individuals,'' she said.

Dr Harri Vainio, of the French International Agency for Research on Cancer, said Finland was one of the few countries with a downward trend in smoking-related diseases. He called for political intervention in other countries.

''It is important to have regulations and even laws in order to do something with smoking because we can do something with voluntary campaigns to help people stop smoking, but what really works is still regulation to stop people being exposed to passive smoking.''

The current incidence of 10 million cancer cases worldwide would double in 20 years, he said, and genetic therapy could do little about that.

Dr Harry Campbell, of Edinburgh University, said it was often assumed that, by specifying risks to individuals, genetic tests would motivate them to change their behaviour. ''However, the opposite may be true. By telling people that they are at genetic risk we may demotivate them.''

Professor Sally Macintyre, of the Medical Research Council's Glasgow-based sociology unit, told the conference, organised by the Royal Society of Edinburgh, that evidence collected over the last five years showed that telling people about the health risks of smoking did not automatically change their behaviour.