The Theory of Unpleasant Symptoms (TOUS) is considered a middle-range theory. According to Lenz (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. Lenz et al. collaborated to publish a combination of Pugh and Gift's concepts as the Theory of Unpleasant Symptoms. In 1997, Lenz published an updated version of the TOUS.
The Theory of Unpleasant Symptoms was proposed as a means to integrate existing information about a variety of disease manifestations. This theory was developed by the collaborative effort of four nurse researchers (Andreu Gift, Renee Milligan, Elizabeth Lenz, Linda Pugh) in 1995 and then improved in 1997. They shared an interest in nature and in clinical practice. It is a theory that emerges spontaneously from the practice of nursing inductively from the particular to the general, reflections from the real world.
Theoretical elements and Concepts of Theory of Unpleasant Symptoms (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”. 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. 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.
The symptom is the first component of theory, and constitutes the starting point of the theory and therefore the central element of this. In turn, symptoms or manifestations of disease are of great significance in palliative care nursing. Symptoms are defined as perceived indicators of change in the normal functioning as experienced by the patient. Thus, consider a subjective experience, therefore, only reported by the patient. This theory posits the experience of one or more symptoms. A symptom may precede and possibly lead to other symptoms. When experiencing more than one symptom at the same time, the perception of these may be higher than if presented in isolation.
These symptom dimensions are influenced by three categories of variables: physiologic factors, psychologic factors, and situational factors. According to Lenz (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 ...