Teenagers who send and receive more than 120 text messages a day are more likely to be into sex, drink and drugs, say the authors of a new study.
Researchers at Case Western Reserve University School of Medicine carried out a confidential survey of more than 4,200 students at 20 schools in Cleveland, Ohio, to find out if texting and social networking are linked to sex and other risky activities.
The answer was a resounding "yes".
The team found those students who sent or received SMS messages at least 120 times a day were nearly three and a half times more likely to have had sex than peers with more moderate texting habits.
So-called "hyper-texters" and "hyper-networkers" - those who spent three or more hours a day on Facebook and other social networking websites - were also more likely to fight, binge drink, take illegal drugs, self-harm, smoke, have an eating disorder, be depressed or to have considered suicide.
Around one in five students was identified as a hyper-texter, and about one in nine was a hyper-networker.
Naturally, the researchers aren't suggesting that a penchant for text messaging will turn your teenage son or daughter into a street-fighting, booze-addled sexaholic - but fleet-fingered phone skills may, they say, be a "red flag" for parents.
"If parents are monitoring their kids' texting and social networking, they're probably monitoring other activities as well," explained Dr Scott Frank, an associate professor of epidemiology and biostatistics at Case Western, who presented the study's results at a meeting of the American Public Health Association in Denver on Tuesday.
"If you wouldn't let your teen go out and socialise for three hours every school night," added Frank, "why would you let them spend the same amount of time socialising from home?"
With all those hours spent texting and updating Facebook profiles, we wonder where they find time to fit in the rest.
And if, like us, you were thinking that 120 text messages a day sounds a lot... chances are, it's an underestimate. A study released last month by analysts Nielsen found that an average teenage girl in the US sends and receives 4,050 texts a month - that's 135 texts a day.