His study found that one in seven became restless if they were away from their phone for a long time, while 14 per cent would be willing to lie to hide the exact time spent on their mobiles. "This is addictive behaviour. You might ask how people can get hooked on mobile phones but you would probably see similar responses if you took away someone's car. They are part of everyday life," Dr Sheffield said. "Getting phone calls can make you feel better about yourself - give you greater self-esteem. Whereas not getting calls can make you feel down or less important."
He tested the blood pressure of 20 students as they yakked on their mobiles and found that the reading was normal when they were without the phones, but shot up once they started talking on it. In another test 106 students answered questionnaires on their mobiles. 16% had problems with the phones, the researcher said.
"You have to take into account this study was carried out specifically on students but it seems large numbers use mobile phones heavily and this has a significant impact on their lives," Dr Sheffield added.