Psychotherapist Andreas Herter has estimated that approximately 380,000 Germans are addicted to text-messaging. Herter, who has also written a sex therapy book said: "Text message addiction is a real and serious illness."

"It causes mental and financial damage. The problem leads to depression and personality disorders, not to mention spiralling phone bills," Herter said yesterday.

Amoung the more serious cases he has seen was a teenaged male who spent 8,900 euros. He couldn't stop texting, sending messages to people he didn't even know. Another case was a married couple who would text each other even while sitting together.