Parents have been warned to watch out for signs of excessive texting in their children, amid concerns it poses a new health risk.
Teenagers sending 120 text messages a day are more likely to drink, smoke and have sex, claims a US doctor.
Scott Frank told a US conference that extreme texting and use of social media is linked to higher levels of risky behaviour.
A UK expert said internet addicts are at risk of other bad habits.
Dr Scott Frank, a physician and public health expert at Case Western Reserve School of Medicine in Cleveland, Ohio, surveyed about 4,000 high school students, aged 13 to 18, at 20 local schools on their texting and social media habits.
Almost 20% were classified as hyper-texters - sending more than 120 text messages on a school day.
Taking into account lifestyle factors and income, they were more likely than other students to have smoked, drunk alcohol, used drugs and had sex, research presented to the American Public Health Association meeting in Denver suggests.