Self Determination Theory (SDT) is a psychological theory of human motivation and personality. It is concerned with the factors that promote and support the natural growth and development of individuals, and with the factors that disrupt or undermine it. SDT proposes that all people have basic psychological needs for autonomy, competence, and relatedness, and that satisfying these needs is essential for well-being and healthy functioning. When these needs are not met, people are more likely to experience negative emotions, such as anxiety and depression, and to engage in unhealthy behaviors. SDT is often used in the design of interventions to promote well-being and healthy behaviors.