The fixed, beaming face of the service sector in Japan could be about to crack: its famous “perma-smile” is slowly driving the country mad.

For hundreds of thousands of women across Japan a well-honed smile is a critical part of their job description. Almost every service business insists that its women staff learn to smile broadly at all times. For youngsters taking up jobs in the huge convenience store industry, the first day of training is spent developing the perfect, customer-luring smile.

The problem, a leading psychiatrist at Osaka University alleges, is that after a while many women simply cannot turn the perma-smiles off.

Real emotions, Makoto Natsume says, are being dangerously suppressed by the “smile masks” that women wear all day at work and the psychological effects he sees among patients are devastating. Depression, mental illness and other disorders are spreading fast, he cautions, and smile-mask syndrome could soon become a serious national health issue.

“Forcing yourself to wear this smile mask for a long period of time can, as it gets more extreme, lead to real depression,” he said. The all-day smiles, he added, are also responsible for a range of physical ailments: among the patients that he has treated with smile-mask syndrome, many complain of painful muscle and head-aches akin to repetitive strain injury.

One new recruit at a Tokyo outlet of FamilyMart described a morning regime devised by her employer where she had to cover the top half of her face and practise smiling with the mouth only and without bringing her eyes into the equation.

A popular game for the handheld Nintendo DS — Face Training — provides a full exercise regime for those who want to improve the quality of their smiles. It has no scheduled release date outside Japan.

Professor Natsume describes conversations with patients in which they have related deeply unhappy episodes in their lives but are shocked to discover afterwards that their smiles never faltered. He believes that the long years of slump crystallised a cultural belief that “men should be brave and women should be winsome”.

Other Japanese commentators have identified a deep social ill in the perma-smiles of the service industry. Tomomi Fujiwara, the author, points out that it was not until the 1980s that Japanese people smiled in the workplace at all. He blames Tokyo Disneyland, which opened in 1983, for giving Japan “perpetual smiles that are the product of manuals”.

Yet corporate Japan still believes wholeheartedly in the power of the smile and is spending more money each year on that belief. Yoshihiko Kadokawa, for example, travels the country as its premier “smile consultant”, earning hefty payments educating the retail industry how to derive greater profits from revealing its teeth.

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