Primary author: Kimberly Seidel

The Theory of Unpleasant Symptoms

The Theory of Unpleasant Symptoms (TOUS) is considered a middle-range theory. According to Lenz et al. (1997), middle-range theories are concrete enough to link research and practice. The TOUS originated based on the development of two concepts, one regarding dyspnea and the other regarding fatigue. When Drs. Linda Pugh and Audrey Gift were combining these two concepts, they found many similarities between their ideas regarding these two symptoms(Peterson & Bredow, 2004). In 1995, Lenz et al. collaborated to publish a combination of Pugh and Gift’s concepts as the Theory of Unpleasant Symptoms. In 1997, Lenz et al. published an updated version of the TOUS.

According to Lenz et al. (1997), the TOUS has “three major components: the symptoms that the individual is experiencing, the influencing factors that give rise to or affect the nature of the symptom experience, and the consequences of the symptom experience”(p. 15). The TOUS asserts that these components interact and influence one another. Additionally, multiple symptoms as the result of a single cause can be considered in combination or alone. According to Peterson & Bredow (2004), symptoms are multi-dimensional including intensity, timing, distress, and quality. Severity and strength of symptoms can be included in the intensity dimension. Time includes frequency and duration of symptoms. The extent to which a symptom bothers a patient is categorized as distress. The quality of a symptom includes a patient’s description of the symptom.

These symptom dimensions are influenced by three categories of variables: physiologic factors, psychologic factors, and situational factors(Lenz et al., 1997). According to Lenz et al. (1997), physiologic factors include the function of body systems, trauma, and energy levels; psychologic factors include mental state and knowledge of symptoms; situational factors include the social and physical environment. All of these factors may impact an individual’s experience with individual and multiple symptoms. The TOUS asserts that these three factors relate to one another and interact with one another to impact symptoms.

Performance is the last component of the TOUS. According to Peterson & Bredow (2004), “performance includes functional and cognitive performance”(83). Social and physical activities and interactions of daily life are considered part of functional performance. A decline in cognitive performance including thinking and problem solving are often seen as the result of symptoms(Peterson & Bredow, 2004). Additionally, the updated version of the TOUS asserts that “performance has a reciprocal relation to the symptom experience. For example, pain can decrease physical activity, which may, in turn, generate even greater pain”(Lenz et al., 1997, 21).

These three components of the TOUS, symptoms, their influencing factors, and consequences, can all be applied to public health issues to aid in the successful design of intervention programs. A desired health outcome can be labeled as a performance in the TOUS. Since performance has a reciprocal relationship to symptoms, it is important to understand not only the symptoms that this health outcome may prevent but also those that the outcome may create. The manner in which situational factors influence symptoms and in turn performance may be of particular interest when considering the study of behavior in public health interventions. Understanding the influence of situational factors on symptoms include understanding the influence of culture, social support, weather, and air quality on symptoms(Lenz et al., 1997). Social networking and social support is important to the TOUS, potentially influencing management of the intensity of symptoms.

Applying the TOUS to theories of behavior change can provide a deeper understanding of concepts within these theories as they pertain to specific behavior change. For example, situational factors that influence intensity and distress of a symptom may help to explain perceived barriers and benefits of a specific behavior. These perceived barriers and perceived benefits are concepts of the Health Belief Model that can be applied to behavior change(Glanz et al., 2008). If a performance, such as physical activity, will decrease the intensity of a symptom, this may increase perceived benefits. However, if this performance will increase the intensity of a symptom it may contribute to perceived barriers.

McCann and Boore (2000) use the TOUS to analyze the specific symptom of fatigue as a result of haemodialysis to treat renal failure. McCann and Boore used the TOUS to address a single symptom and analyze its ties to a specific cause. On the other hand, Pugh and Milligan used the TOUS to aid in intervention design. Specifically, Pugh and Milligan (1998) used the influencing factors outlined by the TOUS to design an intervention to increase the duration of breastfeeding by decreasing fatigue. The TOUS and its interrelated components can be applied not only to individual symptoms but also to public health and the design of public health interventions.

Glanz, K., Rimer, B.K., & Viswanath,K. (2008). Health behavior and health education: Theory, research and practice (4th ed.). San Francisco, CA: Jossey-Bass.
Lenz, E., Suppe, F., Gift, A., Pugh, L., & Milligan, R. (1995). Collaborative development of middle-range nursing theories: Toward a theory of unpleasant symptoms. Advances in Nursing Science, 17(3), 1-13.
Lenz, E., Pugh, L., Milligan, R., Gift, A., & Suppe, F. (1997). The Middle-Range Theory of Unpleasant Symptoms: An Update. Advances in Nursing Science, 19(3), 14-27.
McCann, K., & Boore, J. (2000). Fatigue in persons with renal failure who require maintenance haemodialysis. Journal of Advanced Nursing, 32(5), 1132-1142.
Peterson, S., & Bredow, T. (2004). Middle Range Theories: Application to Nursing Research. Philadelphia, PA: Lippincott Williams & Wilkins.
Pugh, L.C., & Milligan, R.A. (1998). Nursing intervention to increase the duration of breastfeeding.Applied Nursing Research, 11(4), 190-194