If you're using these words a lot, they're a big sign that you're secretly stressed.

Mood swings, poor sleep and frequent headaches are common symptoms of stress. But new research published in the Proceedings of the National Academy of Sciences has identified a startling relationship between the words we use and our stress levels.

After collecting the conversations of almost 150 individuals, the researchers found that among stressed individuals, the same words kept coming up.

Speaking to Nature.com, Matthias Mehl, a psychologist, became interested in how people used function words, such as adverbs and pronouns, to subconsciously express their emotions.

Why was that important?

Mehl said that on its own a pronoun or adverb could mean anything, but placed in context, it clarifies the intensity or emotion behind something. They are also more likely to uttered without you thinking about it.

“[They] are produced more automatically and they betray a bit more about what’s going on with the speaker,” he told Nature.com.

After transcribing the conversations of these people, and comparing them against their gene expressions, which indicated their stress levels, researchers found the more ‘stressful’ words.

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Words like ‘so’, ‘very’ ‘really’ and ‘incredibly’ sound the alarm of a stressed person. Considered “emotional intensifiers”, these words can indicate the degree of how something is being felt.

For example, “I’m feeling nervous about the meeting with my boss,” versus, “I’m feeling incredibly nervous about the meeting with my boss.”

Those types of adverbs qualify the level we feel something.

Interestingly, researchers found stressed-out individuals were less likely to talk - at all. And, their use of third-person pronouns, like 'their' or 'they' drop.

This could possibly be explained by people thinking more about themselves when stressed and less about others.

While the researchers say it's not your sure-fire method to predicting someone's stress levels, it's an important reminder that our language can let on more than we know.

Next time you ask someone if they're okay and they respond,"Yes, I really am, fine. Totally! Incredibly busy, but really, truly fine," maybe ask again. Because it might not be so easy for someone to hide their true angst, after all.