Application of the Theory of Unpleasant Symptoms in Practice: A Challenge for Nursing

Investigación en Enfermería: Imagen y Desarrollo, vol. 20, no. 1, 2018

Pontificia Universidad Javeriana

Elizabeth R. Lenz

The Ohio State University, Estados Unidos

Symptoms are at the heart of nursing care. Much of what nurses do for and with patients is focused on symptoms: measuring them, assessing factors that may influence changes, developing prevention and management strategies, and helping patients with ongoing monitoring and self-management. The Theory of Unpleasant Symptoms (TOUS) was developed to highlight important aspects of the symptom experience in order to improve understanding and help guide nursing research and practice. It is exciting that interest in the theory and its application has been increasing internationally.

The TOUS has three major related parts: the symptom(s), factors that influence the symptom (influencing factors), and the performance outcome. The theory defines symptoms subjectively, as perceived by the patient. Symptoms are proposed to vary in intensity, timing (e.g., time of onset, duration), the distress that the patient experiences, and quality (how they feel). Two or more symptoms can occur together, a phenomenon currently identified as a symptom cluster. Multiple symptoms occurring together may have the same or different causes, and can have cumulative or multiplicative effects. By categorizing influencing factors as physiological, psychological, and situational, the TOUS encourages thinking beyond the physical realm of care. Physiological factors include age, gender, and variables related to the illness(es) and treatments. Psychological factors include mood and cognition (for example, knowledge about and understanding of the illness). They exert strong influence on symptoms. Situational factors are external to the individual. They emphasize the potential impact of the physical and social environments on the patient. The outcome of the symptom experience is performance, which is defined broadly to include physical, cognitive, and social role performance (1,2).

The TOUS emphasizes the complexity of symptoms, while also implying possible preventive and management strategies. According to the theory, the three related categories of influencing factors affect the occurrence of one or more symptoms and how they are experienced. The symptom(s), in turn, affects the individual’s performance, which can feed back to influence the symptom experience and the influencing factors. The theory does not include explicit interventions. Instead, it is assumed that many of the components and relationships in the TOUS could be targeted for intervention.

Several studies have applied the TOUS in practice with positive results. It should be noted that these applications have had multiple components, and all include teaching of the patient and family caregivers. Some of the practice applications that would be consistent with the theory include the following.

  1. Symptom assessment would address not only intensity, but also timing, distress and quality; it would go beyond the symptoms typically associated with the patient’s presenting illness, and it would be ongoing in order to monitor change.

  2. The intake history would be comprehensive, addressing possible psychological and environmental, as well as physiological influences.

  3. Interventions would address the influencing factors that are amenable to change, including psychological issues, particularly anxiety and depression; multiple intervention strategies would likely be required.

  4. Performance outcomes would be assessed regularly to monitor change.

  5. The plan of care would include regular short- and long-term symptom and performance monitoring, and instruction to encourage patient self-monitoring and self-care.

Some challenges would be likely to face those nurses attempting to apply the TOUS in practice. First, practicing nurses often do not view theory of any kind as helpful, in part because many theoretical frameworks are too abstract and esoteric to provide guidance. Therefore, a first step would be to provide instruction about the TOUS, as well as to supply convincing evidence of its practicality and the ease with which it can be understood. Secondly, the TOUS emphasizes that successful symptom prevention and management require going beyond standard physical care. Several successful applications of the theory have involved multi-professional teams and are quite complex. Teamwork is never simple. It is more time-consuming than individual decision-making and action. It requires enthusiastic, committed leadership, and excellent and frequent communication and coordination. Third, given its complexity, applying the entire TOUS at once would require more effort and expense than is generally feasible. Portions of the theory could be applied. Decisions about which aspects to apply would ideally involve prior agreement by team members about professional and patient priorities. Fourth, applying the theory ideally entails many measures that would be repeated over time. Therefore, the instruments to be used would need to be selected carefully, assuring strong reliability, validity, efficiency, and practicality, while minimizing patient and caregiver burden.

The origins of the TOUS were in practice; therefore, it is amenable to application. Smith and Liehr (3) categorize it as a theory that is “ready for application.” Examples of the clinical applications are expanding to encompass more and more symptoms, clinical populations, and settings. Despite this progress, a challenge to those wishing to apply the theory continues to be a shortage of published evidence to help guide applications. Therefore, we encourage nurses and their colleagues not only to apply the TOUS in practice, but also to publish accounts of the experience and the results of those applications in both clinical and research journals. This information will be essential to refining the theory, advancing symptom science and improving patients’ lives.


1. Lenz ER, Pugh LC, Milligan R, Gift A, Suppe F. The middle-range theory of unpleasant symptoms: An update. Adv Nurs Sci. 1997;19(3):14-27.

2. Lenz ER, Pugh LC. The theory of unpleasant symptoms. In Smith MJ, Liehr PR, editors. Middle range theory for nursing 3rd ed. New York: Springer; 2014. p. 165-95.

3. Smith MJ, Liehr PR.Middle range theory for nursing. 3rd ed. New York: Springer; 2014.