Staff who are always complaining could be suffering from a medical condition similar to post-traumatic stress.
A two-year study of workplace anxiety in Germany has indentified an illness the researchers have called post-traumatic embitterment disorder.
Those most susceptible lead lives that revolve around their work - especially if they are passed over for promotion, feel undervalued by their colleagues or are humiliated in the workplace.
Symptoms include pulling 'sickies', feelings of depression, aggression or helplessness, a poor appetite, nightmares and phobias about people and places linked to work.
Those who paid more attention to other areas of their lives, such as family and hobbies, are less likely to be affected.