Introduction The study ‘Mental healthcare provision for adults with intellectual disability and a mental disorder’ (MEMENTA) is a cross-sectional epidemiological study carried out in three different regions of Germany. Its main aim is to assess the prevalence of mental disorders in adults with intellectual disability (ID) as well as quality of mental healthcare for this population.

Methods and analysis The target population are persons aged between 18 and 65 years with a mild or moderate ID. The study population will be recruited through service providers. A representative sample is realised by two-stage sampling. First, institutions providing services for people with ID (sheltered workshops) are selected in a stratified cluster sampling, with strata being (1) types of service-providing non-governmental organisations and (2) sizes of their sheltered workshops. Then persons working in selected sheltered workshops are selected by simple random sampling.

An estimated number of 600 adults with ID will be included. Information will be obtained from the group leaders in the sheltered workshops, informal carers or staff members in sheltered housing institutions and the person with ID. Besides the main outcome parameter of psychiatric symptomatology and problem behaviour, other outcome parameters such as needs for care, quality of life, caregiver burden, health services utilisation and costs for care are assessed using well-established standardised instruments. If a comorbid mental disorder is diagnosed, quality of mental healthcare will be assessed with open questions to all interview partners and, in addition, problem-focused interviews with a small subgroup. Analyses will be carried out using quantitative and qualitative methods.

Ethics and dissemination Approval of all three local ethics committees was obtained. Research findings will add much needed empirical information in order to improve services provided to this vulnerable group of patients.

Trial Registration number NCT01695395.