European researchers report that teenagers who use their phones more than 15 times a day have more trouble falling asleep and staying asleep than those who use their phones sparingly.
Heavy cell phone users are also more likely to be stressed out and generally feel tired, says Gaby Badre, MD, PhD, of Sahlgren's Academy in Gothenburg, Sweden, and the London Clinic, in England.
The findings apply to both excessive chatting on the phone and text messaging, he tells WebMD.
The study, which Badre says is the first to look at the psychosocial effects of excessive mobile phone use, was presented here at SLEEP 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies.
Anecdotal Reports Link Cell Phone Use to Anxiety
Badre says he decided to perform the study after hearing anecdotal reports that people who spend more than an hour a day on their cell phones tend to suffer from anxiety.
The researchers studied 21 healthy teens, aged 14 to 20, with regular working or studying hours and no sleep problems.
Ten of the adolescents were light users, making or sending fewer than five calls and/or text messages a day.
The 11 heavy users made or sent more than 15 calls and/or text messages a day. Four of them sent more than 30 text messages a day, and one sent more than 200.
Badre says he was "amazed" that only one of the teens, a light user, turned his phone off at night.
Participants were asked more than 40 questions regarding their lifestyle and sleep habits -- how much they sleep, how long they sleep, how much caffeine they consume, and so on. They were also asked to rate how sleepy they felt during the day on a standardized scale.
Additionally, the teens wore a small watch-like device that records movement, "thereby giving us an objective measure of when they were awake and when they were asleep," Badre says.