Stress, much of it caused by the speed of change in the workplace, costs Australian society up to $5billion a year through absenteeism, illness, marital breakdown, violence and suicide. This is the view of Professor Graham Burrows who yesterday chaired a seminar on the issue as a curtain-raiser to the second World Congress on Stress, which officially opens in Melbourne today. Professor Burrows said the problem was not confined to Australia and quoted World Health Organisation figures predicting that by 2020 five of the top 10 medical problems worldwide will be stress-related.