This literature review was carried out to examine the effects of user involvement in shared decision-making processes and the methods/tools available to psychiatric nurses to measure and encourage user involvement. A systematic literature review was then used in this study. Many studies indicate that an increased involvement of service users leads to better care, better treatment compliance, improved health outcomes and higher levels of patient satisfaction. The tools and methods described are designed to measure the ability to participate, the process of implementation and the evaluation of healthcare services. An adequate instrument to measure user involvement will be necessary to underpin the positive effects. Although care providers have a statutory duty to help shape user involvement, and the tools required are available, care providers are still insufficiently inclined to take up this duty.