Teenagers who use mobile phones "excessively" are more prone to disrupted sleep and restlessness, new research reports.

Findings to be presented today at Sleep 2008, the 22nd annual meeting of the Associated Professional Sleep Societies, will suggest that mobile use among young adults can cause stress and fatigue.

The study by Gaby Badre MD, of Sahlgren's Academy in Gothenburg, Sweden, focused on 21 healthy subjects aged 14 to 20 who had regular working/studying hours and no sleep problems.

The subjects were broken into a control group of three men and seven women, and an experimental group of three men and eight women.

The control group made fewer than five calls and/or sent five text messages a day, while the experimental group made more than 15 calls and/or sent 15 text messages a day.

The subjects were then asked questions about their lifestyle and sleep habits.

When compared to subjects with restricted use of mobile phones, young people with excessive use of cell phones (both talking and text messaging) suffered increased restlessness.

They were also found to have more careless lifestyles, more consumption of stimulating beverages, difficulty in falling asleep, disrupted sleep and more susceptibility to stress and fatigue.

"Addiction to mobile phones is becoming common. Youngsters feel a group pressure to remain connected and reachable round the clock. Children start to use mobile phones at an early stage of their life," said Badre.

"There seems to be a connection between intensive use of cell phones and health-compromising behaviour such as smoking, snuffing and the use of alcohol. "

The researcher believes that it is vital to increase the awareness among youngsters of the negative effects of excessive mobile phone use.