Article in the SMH says: "Researchers at a German university - a land where surliness is an Olympic discipline -say enforced jolliness on the job is much more likely to make people fall ill.
They cite flight attendants, sales personnel, call centre operators, waiters and others in contact with the public for extended periods of time as being at risk of seriously harming their health.
Psychologists at Frankfurt University said the fake friendliness led to depression, stress and a lowering of the immune system itself, which in turn can trigger more serious ailments..."
W: http://www.smh.com.au/news/seniorshealth/secret-to-a-long-life--get-even-more-often/2006/03/21/1142703333722.html