Scientists are still figuring out the potential downsides of having the miniature computers known as smartphones forever in our pockets, but the research so far suggests that these devices are having a long-term detrimental effect on both our posture and mood.

The trouble is that looking at a phone usually requires hunching over and looking down, unless you regularly hold your phone at eye level. This means we're putting around 27 kg (60 pounds) of extra strain on our neck. As it so happens, researchers have found that the posture we adopt when looking at our phones is similar to the posture that people suffering from depression adopt. It can be difficult to tell the difference between the people who are miserable and staring at their feet and those who are simply flicking through Twitter.

As Amy Cuddy at The New York Times notes, posture can cause negative emotional states as well as reflect them. A study published earlier this year found that when people were forced to slouch, it had a negative effect on mood and self-esteem. Another report showed that slouching can cause some memory loss, whereas sitting up straight helps us retain more information - another good reason to aim for the correct posture.

What's more, a quick test by Cuddy and one of her colleagues at Harvard University found that people using smaller devices - those who have to slouch over more - became less assertive. This all points to the damaging effect that smartphone use can have, both on the pressure on our bodies and the mental consequences that go along with that.

"Ironically, while many of us spend hours every day using small mobile devices to increase our productivity and efficiency, interacting with these objects, even for short periods of time, might do just the opposite, reducing our assertiveness and undermining our productivity," writes Cuddy. "Your physical posture sculpts your psychological posture, and could be the key to a happier mood and greater self-confidence."

She suggests avoiding the practice of hunching over smaller screens where we can, and using larger devices whenever possible. It's also a good idea to regularly run through a series of exercises that stretch the back, shoulder, and neck muscles.

Scientists are still exploring the long-term effects of smartphone use - remember that the iPhone didn't launch until 2007 - but there's already plenty of evidence that these little boxes of tricks have potential health risks as well as many benefits. Perhaps we'll have to wait for augmented reality glasses to hit the mainstream before we can save the strain on our necks and shoulders.