Melbourne/Washington, Jan 22 (IANS): Australian researchers have discovered how social media can serve as an indicator of a community's psychological well being and can predict rates of heart disease.

Researchers from the University of Pennsylvania and the University of Melbourne, Australia, demonstrated that micro-blogging site Twitter can capture more information about heart disease risk than many traditional factors combined as it also characterises the psychological atmosphere of a community.

They found that expressions of negative emotions such as anger, stress and fatigue in a county's tweets were associated with higher heart disease risk.

On the other hand, positive emotions like excitement and optimism were associated with lower risk.

"The relationship between language and mortality is particularly surprising since the people tweeting angry words and topics are in general not the ones dying of heart disease. This means if many of your neighbours are angry, you are more likely to die of heart disease," said Andrew Schwartz, visiting assistant professor in the School of Engineering and Applied Science at Penn.

Drawing on a set of public tweets made between 2009 and 2010, the researchers used established emotional dictionaries to analyse a random sample of tweets from individuals who had made their locations available.

There were enough tweets and health data from about 1,300 counties, which contain 88 percent of the country's population.

As there is no way to directly measure people's inner emotional lives, the team drew on traditions in psychological research that glean this information from the words people use when speaking or writing.

Having seen correlations between language and emotional states, the researchers went on to see if they could show connections between those emotional states and physical outcomes rooted in them.

They found that negative emotional language and words like "hate" or expletives remained strongly correlated with heart disease mortality even after variables like income and education were taken into account.

Hostility and depression have been linked with heart disease in past studies. Negative emotions can also trigger behavioural and social responses.

"You are also more likely to drink, eat poorly and be isolated from other people which can indirectly lead to heart disease," added Margaret Kern, assistant professor at the University of Melbourne, Australia.

The study, published in the journal Psychological Science, was led by Johannes Eichstaedt, graduate student at Penn.