iPhone users crumble without their digital companions. Flickr/TheeErin Researchers at the University of Missouri have found that iPhone users lose the plot when they're without their much-loved devices.

The University of Missouri (MU) has published a study that shows iPhone separation causes "serious physiological and psychological effects" and leads to poor performance in cognitive tests.

The researchers behind the study even go as far to say that iPhones are capable of becoming "extensions of our selves" — and that we fall into a negative physiological state when they're far away. MU also suggests that when we're doing important tasks, we shouldn't be without our iPhones, as otherwise things go badly wrong.

Published on Jan. 8, the study reveals analysis that was carried out on 40 iPhone users to better understand the impact of smartphone usage and "specifically what happens when people are separated from their phones".

MU explains its team asked iPhone users to sit at a computer cubicle in a media psychology lab. Participants were told the experiment was actually to test the reliability of a new wireless blood pressure cuff — when in fact they were under the microscope to see just how reliant on their iPhones they are in daily life.

The participants had to complete a word search puzzle — first with their iPhone by their side, MU writes, and then without it. The group was told their phones were causing "bluetooth interference" for the second half of the study when they had to part with their devices. Their heart rates and blood pressure levels were monitored — and the people also recorded their own levels of anxiety and how unpleasant they felt during both tasks.

Russel Clayton, a doctoral candidate at MU and lead author of the work, says on the MU website: “Our findings suggest that iPhone separation can negatively impact performance on mental tasks. Additionally, the results from our study suggest that iPhones are capable of becoming an extension of our selves such that when separated, we experience a lessening of ‘self’ and a negative physiological state.”

Clayton worked with the University of Oklahoma's Glenn Leshner and a doctoral student from Indiana University-Bloomington on the project.

The team writes: "The researchers found a significant increase in anxiety, heart rate and blood pressure levels, and a significant decrease in puzzle performance when the participants were separated from their iPhones as compared to when iPhone users completed similar word search puzzles while in possession of their iPhones."

The findings underpin just how addicted we've become to technology. Researchers say that being apart from your iPhone could result in "poor cognitive performance" when doing things like sitting tests, attending conferences, or taking part in meetings