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Japanese men have been locking themselves in their bedroom in increasingly large amountsGetty Images

Japanese health authorities are trying to tackle a growing epidemic sweeping across the nation – a condition where hundreds of thousands of people lock themselves in their bedroom and refuse to leave.

The ailment, known as hikikomori, is thought to affect up to one million people in the country – the majority of whom are men.

Kyushu University's Dr Takahiro Kato, one of just a handful of experts on the condition, told Australia's ABC: "In Western societies, if one stays indoors, they're told to go outside. In Japan they're not.

"Our play has changed, it's all on screens and not real-life situations any more. There are cultural reasons also, a strong sense of embarrassment and an emotional dependence on the mother."

Kato added that "hikikomori is not just about mental illness.

"We're working on the social and biological aspects as well and want to be the first to provide a multi-dimensional diagnosis."

A former sufferer of the condition, Yuto Onishi, told ABC that he would only leave his room when he thought he was safe from social interaction in order to sneak food in the middle of the night.

Onishi: "Once you experience it, you lose reality. I knew it was abnormal but I didn't want to change.

"It felt safe here."

Kato told ABC that family support and working on one's relationships with others is vital to overcoming hikikomori. He continued: "Facing your trauma is horrifying, it's hard to do.

"If you can do it with somebody else, then they can show you a different vision of the future."