Image caption There are risks and benefits to sharing your emotions online

Decades of research have shown that writing down your emotions has concrete health benefits - even helping wounds heal. But as more and more people publish their intimate feelings online, could they be doing themselves more harm than good?

High-profile coverage of cyberbullying might make sharing your deepest emotions online sound like a bad idea, but when it comes to the risks and benefits of writing online, advice is mixed.

The American Academy of Pediatrics, for example, suggests questions about social media are included in visits to the doctor, a move prompted by worries about cyberbullying, internet addiction and sleep deprivation.

On the other hand, blogging about health problems has been shown to improve feelings of social support, especially when that support is lacking from family and friends.

Traumatic experience

Exploring the connection between well-being and writing down your emotions goes back decades.

In 1986, long before the ubiquity of blogs and social media, Prof James W. Pennebaker published seminal research showing expressive writing could make people healthier.

He had the idea after finding that people who had had an early traumatic sexual experience were more likely to suffer health problems later in life, including cancer and high blood pressure.

Talking to Health Check's Claudia Hammond, Prof Pennebaker said he realised it was because that experience was a secret.

Image caption Writing down your deepest feelings can even help your physical health

"That just led me to ask the obvious question... if secrets are so bad, what if we brought people into the lab and had them in some way just disclose them?"

He asked college students to write on four consecutive days, for 15 minutes each time.

One group were asked to write about the most traumatic experience of their lives, ideally one that was a secret, while the other wrote about superficial things, such as the shoes they were wearing.

'Emotions bottled up'

Tracking their visits to the student health centre in the months before and after writing, he found that the group who wrote about a traumatic experience went only half as much as those who wrote about superficial things.

Professor Laura A. King, who edits the Journal of Personality and Social Psychology, says this research finally proved what people had suspected all along.

I do think people are connecting differently than they have in the past Prof James W. Pennebaker, Department of Psychology, University of Texas, Austin

"Everyone sort of had this idea: if you keep your emotions bottled up it's going to make you sick, or you're going to get an ulcer, or you're going to have a psychological disorder. And Jamie's work was really the first time that people had evidence that this was the case."

Prof Pennebaker's work inspired a generation of psychologists to research the health benefits of expressive writing.

Not every study replicated his result, but many did, including some with truly remarkable results: a recent New Zealand study, for example, found that when older people wrote about traumatic experiences two weeks before having a skin biopsy, their physical wounds healed nearly twice as quickly.

In today's world, however, where emotions are shared freely on blogs and social media updates, might the benefits of expressive writing be wearing off?

A study in 2006 that did not show strong results gave Prof Pennebaker pause for thought.

"They got very weak effects, and I hate hearing that. But it doesn't shock me, because I do think people are connecting differently than they have in the past."

Heartfelt blogs

Yet some research shows that writing about difficult experiences online can be helpful.

Teenagers with social-emotional difficulties benefited from writing about their thoughts and feelings in blogs, researchers at the University of Haifa in Israel found.

Participants were assigned to one of six groups, including one that wrote in blogs open to readers but closed to comments, another in blogs open to comments, and one group that kept private computer diaries.

Though writing about their feelings helped all the groups, those who wrote in the blogs that were open to comments were helped most.

This contrasts with one of Prof Pennebaker's recommendations for expressive writing - to do it for yourself.

But Prof Azy Barak, one of the study's authors, says he was not surprised by the results.

"I think online writing is individually perceived and felt as a private experience, despite its actual openness and publicity."

There is a risk that heartfelt blogs might elicit harmful negative responses, and Prof Barak emphasises that monitoring is essential with therapeutic blogging.

'Get involved in life'

However, they did not find it was a big problem in their study. Out of hundreds of comments, only a few were deleted for being abusive.

"Quite the opposite - we were impressed by the many readers who volunteered to help bloggers in emotional distress."

James Pennebaker's top tips for expressive writing Ask yourself if you need to write. If you find yourself thinking about something too much, dreaming about it or obsessing about it in some way, writing could be beneficial.

Promise yourself you'll write for a minimum of 15 minutes a day for three or four days.

Don't worry about spelling.

Write for yourself, not for an audience: this is not a letter to someone, this is for you.

Plan on destroying what you've written, though whether or not you actually destroy it doesn't matter.

Thoughtfully written and carefully monitored written blogs are not the same as the unbridled world of social media emoting.

Prof Pennebaker himself jokes that in ten years he can imagine a new therapy of "Shut up - keep it to yourself!"

But he thinks that even in a world that tends to wear its heart on its sleeve, people's individual differences are the key to whether expressive writing can help.

People who are very controlled could still benefit from writing, but for those who ruminate about a negative event as soon as it happens a better strategy might be simply to stop it.

"Try to get involved in life, in events and actions where you're not able to think about it as much."