A large Australian study suggests that feelings of loneliness could lead to other mental health problems such as depression, social anxiety, and paranoia.

The paper, which followed more than 1,000 people over a six-month period, also found that those suffering from social anxiety were more likely to be lonely in the future.

It's important to note that correlation doesn't equal causation, and there could be other factors involved here. But the researchers hope that the research will encourage further study into the way some mental health issues and loneliness can be entwined.

Although it's easy to think that depression and loneliness are two sides of the same coin, the two are actually psychologically distinct - while loneliness relates specifically to relationships, depression encompasses more general mental health issues.

As lead researcher Michelle Lim from Swinburne University of Technology wrote for The Conversation last year,

"Loneliness is commonly used to describe a negative emotional state experienced when there is a difference between the relationships one wishes to have and those one perceives one has.

The unpleasant feelings of loneliness are subjective; researchers have found loneliness is not about the amount of time one spends with other people or alone. It is related more to quality of relationships, rather than quantity.

A lonely person feels that he or she is not understood by others, and may not think they hold meaningful relationships."

In her latest research, they took 1,010 people from the general community between the ages of 18-87, and measured changes to their mental health using three online surveys over six months.

After adjusting for prior mental health issues, and other traits, they found that although loneliness could increase the risk of a person developing a mental health issues, the mental health issues themselves didn't usually seem to increase the risk of loneliness.

In fact, only social anxiety increased someone's risk of loneliness - depression and paranoia weren't more likely to make people feel more alone in the future.

This could be because those suffering from social anxiety are more likely to avoid social interactions that could otherwise alleviate the loneliness.

"We are not designed to be alone. We are a social species," Lim said. "Loneliness can also lead to poorer physical health, including increased chance of developing Alzheimer's, have poorer cardiovascular health and poorer immunity."

The researchers are now looking into ways to limit loneliness, and are working on an app for university students and those suffering mental illness.

The research was published in the Journal of Abnormal Psychology in April.

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