BackgroundEnvironmental changes can be positive in mental illness. Systematic, planned and guided environmental change in all its aspects is called nidotherapy. It has shown some benefit but has not been extended to whole communities.AimsA cluster-randomised step-wedge trial is planned in six village communities in Nottinghamshire, England, covering an adult population of 400.MethodAdults in six villages will be offered a full personal environmental assessment followed by agreed change in different 3-month periods over the course of 1 year. All six villages have populations between 51 and 100 residents and are similar demographically. Assessments of mental health, personality status, social function, quality of life and environment satisfaction will be made. After the initial baseline period of 3 months, two villages will be randomised to nidotherapy for 3 months, a further two at 6 months and the last two at 9 months.ResultsThe primary outcome will be change in social function; secondary outcomes include health-related quality of life, anxiety and depressive symptoms, personality status, costs of nidotherapy and life satisfaction. Adverse events will also be recorded. The analysis will be carried out using a multimodal statistical approach examining (a) the change in scores of the primary outcome (social function); (b) change in scores of all secondary outcomes, including costs; and (c) changes in environmental satisfaction.ConclusionsThe findings of this study should help to determine whether nidotherapy has a place in the early detection and treatment of mental pathology.