A new study has found that the average person is holding onto 13 secrets, five of which they've never told a living soul. And it's not the secret itself that will haunt you - it's all the mental energy you spend thinking about it. 

Scientists have found that the burden of having secrets can affect you in ways you might have never considered - some people actually feel physically heavier when they're burdened with a secret, and that extra 'weight' can skew how you navigate your surroundings.

"People have this curious way of talking about secrets as laying them down or unburdening them," lead researcher, Michael Slepian, a professor of management at Columbia Business School, told The Atlantic.

"We found that when people were thinking about their secrets, they actually acted as if they were burdened by physical weight. It seems to have this powerful effect even when they're not hiding a secret in the moment."

Slepian and his team examined 13,000 real life secrets recorded across 10 previous studies to figure out what people are keeping secrets about, what it's like to have a secret, and why secret-keeping has overwhelmingly been viewed as a negative human experience. 

What they were particularly interested in examining was the long-held assumption that secrets can be harmful both to a person's physical and mental well-being - previous research has linked secrecy to depression, anxiety, and poor physical health.

But is it the content of the secret itself that's so dangerous, or the simple fact that we humans respond terribly to keeping anything hidden?

The researchers condensed their 13,000 secrets into 38 common categories of secrets, and presented them to 2,000 new participants.

These categories involved things like telling a lie, harming someone, drug use, theft, violating someone's trust, sexual infidelity, a secret hobby, and sexual orientation.

When the participants were asked if they were keeping secrets related to any of these categories, they found that the average person was currently keeping 13 of the 38 secrets - five of which they have never told anyone about.

As The New Yorker reports, the study found that for the average person, there's a 47 percent chance that one of his secrets involves a violation of trust; a more than a 60 percent chance that it involves a lie or a financial impropriety; and a 33 percent chance that it involves a theft, a hidden relationship, or discontent at work.

The team then asked the participants how often their minds wandered to think about those secrets in the past month, and how often they found themselves in situations that forced them to actively conceal these secrets.

The results showed something completely unexpected - secrets were far more likely to come to the fore when people were alone with their thoughts than in social situations, meaning we spend way more mental energy mulling over our secrets on our own time than actively trying to conceal them. 

They also found that there was no predictor in terms of the content of the secret for how much it would affect someone - in other words, there's no 'moral scale' that says some secrets are universally more consuming than others.

"A conventionally big secret that may be preoccupying and all-consuming for one person, another person can shrug off," Slepian told The New Yorker.

"It became clear that what really determines whether these effects occur is how preoccupied people are by their secrets. When we saw that, it struck me that maybe we've been thinking about secrets in the wrong way."

This suggests that the harm secrets cause is less to do with the fact that we feel guilty about having to constantly conceal them from our friends and family, and more to do with our own preoccupation with them.

"To date, scholars have largely assumed that secrets have their effects because interpersonal withholding is taxing. Our work suggests that, when it comes to secrecy, acts of concealment may be a less potent driver of diminished health and well-being than previously assumed," the researchers report.

"We find that active concealment is rare relative to the many times the mind wanders to thoughts of the secret, and frequency of mind-wandering to, but not concealing, secrets predicts lower well-being."

The research ties into a previous study by Slepian, which looked at how secret-keeping affected people's concentration in other areas.

He found that the "burden" of keeping a secret is more real than it might appear, because it appears to make physical activities seem more difficult than they actually are. 

When participants were asked to judge the slope of a hill or the length of a distance, those who were preoccupied with keeping secrets judged the hills as steeper and the distances longer than they really were.

When they were asked to toss a beanbag at a target, the secret-keepers consistently over-threw their bags, suggesting that they assumed the task would take more effort than it actually did.

"We found that when people were thinking about their secrets, they actually acted as if they were burdened by physical weight," Slepian told The Atlantic.

The psychological research into secret-keeping is surprisingly scarce, largely because of the nature of the thing you're trying to investigate - it's not a secret if you tell a bunch of scientists about it, right? 

But Slepian says that for the sake of our collective well-being, perhaps it's better to think about secrets as something you have, rather than keep.

For many of us, we might never find ourselves in a situation where we're pressured to spill the beans about our biggest secret, but it's always there, lurking at the back of our minds.

If we can figure out how to deal with secrets on our own terms rather than everyone else's, maybe that weight on our shoulders won't hang so heavy.

The study has been published in the Journal of Personality and Social Psychology.