This report provides a comprehensive overview of psychological principles within the context of health and social care. It begins by exploring lifespan development theories, including stage, open-ended, continuity, and discontinuity theories, and how these relate to different life stages such as infancy, childhood, adolescence, and adulthood. The report then delves into specific psychological theories like Piaget's theory of cognitive development and Erikson's stages of psychosocial development, detailing their key features and implications for health and social care settings. Further, the report analyzes the influence of social and biological factors on human behavior, using a case study to illustrate how these factors interact. It also emphasizes the importance of social roles in health and social care, particularly in the context of individuals facing mental health challenges such as Alzheimer's disease. The report concludes by examining the application of psychological theories to understand behavior disturbances, mental disorders, and relationships within health and social care, offering insights into how these theories inform effective care practices.