According to the most recently available Labour Force Survey for 2004-2005, 509,000 individuals in the UK believed they were suffering from stress, depression or anxiety and these conditions were caused or made worse by their current or past work. This resulted in an estimated 12.8 million working days lost with an average of 30.9 days off over a 12 month period. Those employed in the public sector had some of the highest rates of self-reported stress, anxiety and depression. In particular those with heavy workloads, tight deadlines, lack of support at work, in a threatening environment are recognised as being at an increased risk of stress, depression or anxiety. This review aims to determine which workplace interventions are effective and cost-effective in improving mental wellbeing.