It is absolutely in employers' interests to have their employees fit and well. When someone has a physical illness or has broken a limb, it is easy to empathise and understand that the individual needs time off to recover and become fit and well again.
Yet mental health problems do not attract the same level of empathy in the workplace. If anything there is still a huge amount of stigma attached. The article below states that 'two thirds of managers [in the UK] don't believe that stress, anxiety or depression is a serious enough reason for employees to take time off work'. That to me is a very worrying statistic. In an ever changing world, full or uncertainty and increasing pressures, mental health has never been more relevant. For employees to function and give their best, it goes without saying that they need to be both mentally and physically fit - so managers must re-shift their focus and understand that just because an illness is not 'visible' does not mean it has serious health implications for the individual concerned.
My view is that mental health issues are 'visible' it's just that they are not as easy to spot. Managers need to be alert to those signals and understand what steps they can take to assist the employee - it is not about being a counsellor, it is about showing the employee the support available. It's also about addressing the stigma and demonstrating that as a manager you are approachable and prepared to listen and take mental health issues seriously.
There is clearly still a lot of work to be done in this area - the more attention it attracts, the more awareness that is raised, the better.