This data set contains a number of variables collected from participants in the CFS in the NHS trial at assessment and follow up. It does not include data on age and gender as we want to be certain that no participant can be identified through the data. Researchers can apply to access a fuller data set (https://data.bris.ac.uk/data/dataset/3nfgkcm2ce6eg28rt02u86murj) containing age and gender through application to the University of Bristol's Data Access Committee, please refer to the data access request form (http://bit.ly/data-bris-request) for details on how to apply for access.