A certain amount of worry and stress can be energising. They may act as a natural warning system when something is wrong, and can help people meet deadlines and complete tasks. High levels of both are however counter-productive, and all too common. Generalised Anxiety Disorder (GAD) is believed to affect some two million people in the UK, while the World Health Organisation estimates that half of all cases go undiagnosed. These figures put anxiety only second to depression as a mental health problem. In addition, half a million people in the UK suffer work-related stress (HSE survey) while five million say they feel 'very' or 'extremely' stressed at work. Some people may be so incapacitated by worry that normal living becomes impossible; for example, they may refuse to drive the car in case they crash.