More than 4 million babies are born every year in the United States. About 2.5 million people die. And in a 2011 study of its 15 million smartphone owners, security firm Lookout determined that 9 million phones went missing in that group alone. That’s one phone lost every 3.5 seconds.

Last summer, on the beautiful Greek island of Santorini, Alex Iacobacci was one of the unlucky ones. He and his partner had enjoyed a lovely evening of shopping and dinner, but when they returned to their hotel, Iacobacci, owner of the Avanti salon on Newbury Street, realized his iPhone was gone.

His frantic TSA-style self pat down will be familiar to pretty much everyone, as will the way he ran the movie of his nightbackward, desperately retracing his steps, until there were no more places to look.

“My trip is ruined,” he said. His boyfriend offered his phone as consolation. “What good is it?” Iacobacci thought. “The only person whose number I know is my father’s.”

More than 200 million Americans own mobile phones, nearly half of them smartphones, according to the Pew Research Center. That’s up from 35 percent just a year ago, and as a growing number of us move our lives onto these powerful hand-held devices, a new anxiety has been identified: nomophobia.

It’s an abbreviation for “no mobile phone phobia,” a condition identified by the UK Post Office in a 2008 survey that found that nearly 85 percent of mobile phone users get anxious when they run out of battery, have no network coverage, or — yikes — lose their phone altogether.

California State University, Dominguez Hills psychology professor Larry Rosen has another word for it: reasonable.