Introduction

Mo is a 55-year-old client who is generally in good health. He works full-time for a landscaping company where he maintains lawns and gardens most of the year and shovels and plows in the winter. Recently, Mo has started thinking about how he can stay healthy as he looks toward retirement over the next decade.

The health of clients like Mo is affected by many factors, not solely by their medications, how often they see health care providers, their physical endurance, their family’s health, their health insurance coverage, their level of education, or any other single factor. Nurses use theoretical perspectives to perform comprehensive assessments and to plan effective care in partnership with clients. Theories provide a means to explain phenomena systematically and to guide thoughts and decision-making processes by fostering an understanding of the causal pathways between factors of health and disease (Eriksson et al., 2018). This chapter describes the many influences on health, socio-ecological models (SEMs), and other theories of health and human behavior. Mo appears throughout the chapter as an example of how an individual’s health may be affected by a wide array of circumstances in their personal and professional lives.