The smartphone has become such a common part of life that many feel anxious when they're not around their phones.

Well, now that anxiety has been documented -- Apple users actually feel separation anxiety when they're not near their iPhones.

"The data tell an interesting and unique story about how iPhone separation and the inability to answer one's iPhone during cognitive tasks affects a variety of psychological outcomes," said the study, which was put together by Russell B. Clayton, Glenn Leshner and Anthony Almond and published in the Journal of Computer-Mediated Communication. "The data showed that the inability to answer one's iPhone while it was ringing activated the aversive motivational system (increases in heart rate and unpleasantness), and also led to a decline in cognitive performance."

In essence, when iPhone users find themselves unable to answer ringing phones while attempting to solve simple puzzles and word searches, their heart rates and blood pressure levels increased. Levels and feelings of anxiety and unpleasantness also increased. It was also shown that users who had possession of their iPhones were able to better complete puzzles than those who did not have possession of their phones.

"In contrast, when participants completed word-search puzzles with their iPhone in their possession, heart rate and blood pressure levels returned to baseline and cognitive performance increased," continued the study.

Researchers first recorded how participants felt while completing a puzzle when they had possession of their phones. Next, they were informed that their phones were causing "Bluetooth interference" and that they had to be placed further away in the room. Those participants were then given a second puzzle. During this puzzle, the researchers called the participants' phones. Participants' heart rate and blood pressure were recorded throughout the experiment.

Some argue that the study reveals more about how people feel when their phones are ringing and cannot answer them than how they feel when they simply are separated from their phones.

Russell Clayton, one of the researchers, does acknowledge the limitations of the study, however he notes that he is confident in his findings, saying that those that were separated from their phones did experience negative feelings.

So what should users do if they need to focus on a task? Have their phone on them, of course.

"Our advice would be to carry your iPhone with you," said Clayton in an interview. "But to silence your phone during cognitively demanding tasks (i.e., work, meetings, exams, etc.) in order to avoid any potential distractions that may reduce your attention throughout the day."