For years nervous exam takers and job interviewees have been advised to smile to make themselves feel better.
Sadly it seems there isn't a glimmer of truth in faking a beaming grin to make yourself feel happier and more relaxed.
For a myth-busting review of an old study reveals grinning won't always improve your mood, just as frowning doesn't make you feel unhappy.
A 1998 study asked participants to hold a pen between their teeth, causing them to 'grin', or between their lips, inducing a 'frown'.
They were then shown cartoons and asked to rate how funny they were.