An angry tweet can make a person's emotions very clear but new research released today suggests it can also show a community's risk of heart disease.
Researchers at the University of Pennsylvania analysed 826 million tweets in 1,300 counties in the United States, particularly in the country's north-east.
Dr Margaret Kern said some tweets indicated the person was in a community with a high risk of heart disease, which is the leading cause of death in the US and Australia.
"High risk was associated with a lot of very negative emotion, aggressive words and expletives, words like hate, drama, bored," Dr Kern said.
"Lower risk was actually associated with a lot more positive things, words like wonderful, friends, drink, company."
The study found a correlation in those communities between the tweets and the main risk factors for heart disease.
Dr Kern said the study was not looking at an individual's risk of coronary heart disease but that of their broader community.
"This is looking at the context that people are living in, so it may be indicative of what's going on in a person's environment, what could be risky," she said.
"If a person is around a lot of aggressive angry people, maybe over time they are coping with that with things like smoking and drinking that can increase the risk, so we can't predict just for an individual but it might give us an indication of places we should look to lower the risk.
"It's a lot easier to look at the language people are using on social media than to collect information on diabetes and smoking and other risk factors."
Social media becoming source for health information
The study found areas of states like Pennsylvania and New York were at high risk of coronary heart disease.
"It's a pretty high stress area of the country but things like boredom were actually associated with higher risk," Dr Kern said.
"So what's going on there that could be risky? Unemployment certainly, but also things like the environment - are there parks and things for people to do, ways that people can connect with one another?
"Or are we very much in our workaholic lifestyles where we don't engage with people except to yell at them? That's going to be a very different life pattern."
Dr Kern said a key message of the research was that health information could be gleaned from social media.
"By bringing together social sciences and computer science there's a lot we can learn. It's pointing to methods we can use in the future," she said.
"Social media is out there and it's used a lot by marketers to sell us things.
"We can use that information for good and learn from it, especially about the younger generation who use social media a lot."
Dr Margaret Kern recently moved to Australia and is now conducting similar research at the University of Melbourne.
She said the early results suggested Australians use Twitter differently to Americans and are more sarcastic. And her analysis will need to take that into account.
"Australians use more words like please and thank you and a lot of sports words. We see different language and it's quite possible that the risky words for the US are not the same for Australia because they're used in a different sense."
The research has been published in the journal Psychological Science_._