This report delves into the critical intersection of psychology and health and social care, examining the application of various psychological theories to understand lifespan development and human behavior. It explores prominent theories like those of Freud, Erikson, Piaget, Maslow, and Darwin, relating them to different life stages. The report analyzes how biological and social factors influence behavior within health and social care contexts, emphasizing the importance of social roles in these settings. Furthermore, it investigates the application of psychological theories to individuals experiencing stress, behavior disturbances, and mental health disorders, evaluating principles affecting behavior change. The report provides a comprehensive overview of psychological principles in health and social care, offering insights into the complexities of human behavior and its implications for healthcare practices. The document is a student assignment contributed to Desklib, a platform that provides AI-based study tools for students.