The teenage urge to keep in touch with friends has led to dramatic increases in mobile phone sales and alarm over a new type of communication “neurosis”.

One in four elementary and junior high-school students in Tokyo has a mobile phone, a survey by a leading mobile operator has revealed.

NTT DoCoMo interviewed 600 10 to 14-year-old students between fifth grade in elementary school and second grade in junior high school. A separate survey last year found that more than half of Japan’s high-school students own mobile phones, many of them with Internet access.

Half the children with phones said they were a “lifestyle” requirement and 41.5 per cent said their parents “forced” them to have one. Although the average student spends 3,700 yen (pound;22) a month on their phone, 6.1 per cent of students admitted that they run up monthly bills of between 7,000 and 10,000 yen. (pound;42-60).

The survey was conducted in December and January and has set alarm bells ringing. Such density of mobile ownership among the young has led to a new type of neuross, say sociologists. Japanese teens, in particular, have become fanatical about being “always on tap”.

Many high-schoolers can crank out 40 to 60 words a minute on their phones and are sending 50 text messages a day on their phones.

“Teenagers can be seen taking advantage of every spare minute to touch base with their friends. Many become extremely uneasy if they find themselves unable to contact their peers countless times each day, fearing that they are becoming socially isolated,” writes sociologist Hisao Ishii, author of The Superficial Social Life of Japan’s Mobile Phone Addicts.

The boom in the wireless web also has implications for literacy, experts say. As e-mailing, texting and mobile games are now so popular, reading on the train, once a major source of pleasure for all students is being passed over. One recent survey asked school students to rate their own academic performance; 68 per cent of those who said they scored poor grades owned a mobile phone, compared with 49 per cent of those who said they were making good grades.