Psychological adjustment to disease and treatment: A general model

Disease and its related treatment constitute major stressors for many patients. The experience of disease-related stress elicits a psychological adjustment process which, depending on how patients respond, can lead to either improvement or deterioration of health. This adjustment process may be supported by healthcare interventions, examples of which include self-management support, supportive care, or rehabilitation. Over the years, diverse models have been proposed to characterise the adjustment process. These models share similarities, such as the common assumption that cognitive responses to disease will impact health. They also show major differences. For example, some models highlight the role of physiological responses, while others ignore physiological responses altogether. Differences such as these can lead to an unduly narrow perspective on the process of adjustment to disease and treatment. The central tenet of this paper is that existing models can be integrated into a general model of adjustment to disease and treatment. The present article first briefly outlines previous models and then describes a general model of adjustment to disease and treatment, as well as its advantages. Numerous models of adjustment to disease have been formulated. The following section focuses on and briefly summarises four models of adjustment to disease. Three of these models (the transactional theory of stress and coping, the common-sense model of self-regulation of health and illness, and the allostatic load model (references are provided below)) have been especially influential in shaping theory and research. To the author's knowledge, no other models of such status exist. The fourth model (the working model of adjustment to chronic illness) is an important attempt to integrate some previous models and their many variations. The intent here is to characterise the main features of these models rather than provide an in-depth discussion of the models. In the next section, these central features will be used to build a general model. Transactional theory of stress and coping. According to the transactional theory of stress and coping (Biggs et al., 2017; Folkman, 2020; Lazarus & Folkman, 1984), an individual appraises the environment in relation to his or her personal goals, values, and beliefs. The primary appraisal process, which is a cognitive process, may result in assessment of one's environment as either benign-positive, irrelevant or stressful (indicating harm, loss, threat or challenge) in terms of the individual's well-being. The secondary appraisal process leads to an assessment of the actions (coping) the individual might take in response to an environment that is perceived as stressful or in reaction to the emotional/stress response. In doing so, the individual takes into account both personal factors (e.g., personal resources) and environmental factors (e.g., treatment alternatives). Coping is directed at the environment appraised as stressful, or at the emotional experience of harm, loss, threat or challenge. Successful coping leads to reduced stress responses and fewer negative emotions. Coping, however, may be unsuccessful, leading to an environment appraised as even more stressful or to a worsening of the stress response. The appraisal and coping process is hypothesised to affect adaptational outcomes, such as social functioning, morale, and somatic health. The basic mechanism driving the appraisal and coping process is that 'in order to survive and flourish people must distinguish between benign and dangerous situations' (Lazarus & Folkman, 1984) (page 23). This theory has been commonly applied to characterise the process of adjustment to disease and treatment (Meraz et al., 2023; Schreuer et al., 2006; Stanisławski, 2019). The transactional theory of stress and coping is represented schematically in Figure 1. Schematic representation of the transactional theory of stress and coping. The common-sense model of self-regulation of health and illness. The common-sense model has evolved over the years (Leventhal et al., 2016). According to this model (Diefenbach & Leventhal, 1996; Hagger et al., 2017; Hagger & Orbell, 2003; Leventhal et al., 1984, 1992) the individual creates both cognitive and emotional representations of illness in response to illness-related stimuli (e.g., symptoms). This so-called parallel-process model is a hallmark of the common-sense model: it hypothesises the emotional response to disease as a separate pathway, in parallel with the cognitive response. The individual responds to cognitive and emotional representations (e.g., the expected duration of illness, fear) with coping responses that affect illness and emotional outcomes (e.g., disease state, physical functioning, distress, etc.). Additionally, the individual appraises the impact of coping on these outcomes so that, in various feedback loops, appraisal influences illness stimuli, cognitive and emotional representations, and coping. These processes are moderated by the socio-cultural context and the self-system (i.e., biological and psychological characteristics of the individual). The basic mechanism underlying this model, represented schematically in Figure 2, is self-regulation of current and future health threats (Leventhal et al., 2016). Schematic representation of the common-sense model of self-regulation of health and illness. The working model of adjustment to chronic illness. This model was constructed in an attempt to integrate previous models and their many variations (Moss-Morris, 2013). Illness-specific factors are hypothesised to govern critical events (e.g., symptoms, receiving a specific diagnosis) and ongoing illness stressors (e.g., uncertain future). These events and stressors have the potential to disrupt emotional equilibrium and current quality of life. In order to maintain equilibrium, the individual deploys cognitive and behavioural resources, affecting psychological, physical and social outcomes. These cognitive and behavioural factors can impact outcomes positively or negatively. The overall adjustment process is influenced by personal background factors, as well as social and environmental background factors. A return to equilibrium after critical events or ongoing stressors is the basic mechanism underlying the model. The need to further specify the model for particular illnesses and stages of illness was emphasised (Moss-Morris, 2013). The model is represented schematically in Figure 3. Schematic representation of the working model of adjustment to chronic illness. The allostatic load model. Allostasis is an extension of homeostasis (Yamamoto, 2020). With homeostasis, stability through constancy, the organism detects a deviation from a set point, leading to feedback to return to that set point. With allostasis, stability through change, the organism recalibrates homeostatic parameters to adapt to environmental demands (Juster & Misiak, 2023). Allostatic load refers to the long term results of chronic overactivity or underactivity of allostatic systems (McEwen, 1998). Environmental stressors (originating from work, home, or neighbourhood), major life events, or trauma/abuse can be perceived as stressful. Perceived stress initiates physiological and behavioural responses, leading to allostasis and adaptation. Physiological responses occur in the autonomic nervous system, the hypothalamic–pituitary–adrenal (HPA) axis, and the cardiovascular, metabolic, and immune systems. Individual factors (i.e., genetics, development, and experience) shape both the perception of stress and the physiological response. Successful allostasis results in adaptation. Allostasis can be unsuccessful, however, due to frequent stressors, lack of adaptation to repeated stressors, inability to shut off allostatic responses after a stressor is terminated, or when inadequate responses in some allostatic systems trigger compensatory increases in others (McEwen, 1998). This results in allostatic (over)load, which is 'the wear and tear' of chronic stress. A distinction is made within allostatic (over)load between chemical messengers, cellular events, effects in tissues and organs, and actual diseases or disorders (McEwen & Seeman, 1999). The model has been primarily applied to describe how stress originating from environmental factors, stressors, life events, or trauma 'gets under the skin and skull' (Juster & Misiak, 2023). The allostatic load model, represented schematically in Figure 4, was recently used to conceptualise the stressful effects of disease and treatment, for example (Andreotti et al., 2015; Waliszewska-Prosół et al., 2022). Schematic representation of the allostatic load model. Observations concerning previous models. First, the four models outlined above show considerable similarity in terms of components identified in the adjustment process. All four models highlight a subjective interpretation of disease and treatment-related stimuli, leading to the experience of illness stressors (although the stress and coping model and the allostatic load model refer more broadly to environmental stimuli, life events and trauma, instead of disease and treatment-related stimuli only). All four models identify cognitive and behavioural responses in reaction to illness stressors. Similarly, all four models argue that individual factors influence the adjustment process. Second, these models also have major differences. Physiological responses are a crucial component of the allostatic load model, while they play little or no role in the other models. Emotional responses are considered an outcome in the transactional theory of stress and coping, while in the common-sense model of self-regulation of health and illness, emotional responses are seen as a pathway (mediator) in addition to the cognitive pathway. In the model of adjustment to chronic illness, emotional responses are viewed as the first, essential pathway. In the allostatic load model emotions are mentioned only parenthetically, under the broader term 'behaviour'. Social and environmental background factors influencing the adjustment process are mentioned in three models, while the allostatic load model treats these factors only as a stimulus. All four models identify health as the outcome of the adjustment process, but they differ considerably in their conceptualisation of health. Third, the hypothesised basic driving mechanisms also differ between models, and these include survival (Lazarus & Folkman, 1984), self-regulation of health threats (Leventhal et al., 1992), equilibrium (homeostasis) (Moss-Morris, 2013), and allostasis (McEwen, 1998). Fourth, for each of the models subcomponents within a particular component are proposed, and these subcomponents are categorised in various ways. To give some examples, disease and treatment-related stressors have been variously categorised as internal (e.g., symptoms) or external (e.g., prognostic information) (Leventhal et al., 1992), as acute or ongoing (Moss-Morris, 2013), and as disease-specific or generic (Moss-Morris, 2013). Coping has been categorised as problem-, emotion-, or meaning-focused coping (Folkman, 2020), as reactive or proactive coping, or as the 14 constructs of the brief COPE questionnaire (Carver, 1997). These are examples of the myriad subcomponents and categories proposed to date. Fifth, numerous variants of the four models described can be found in the literature. In these variants additional pathways between model components have been proposed, for example (Hagger & Orbell, 2003), additional subcomponents and pathways have been added, for example (Hagger & Orbell, 2022), or theoretical constructs derived from other theories have been integrated into a specific model, for example (Breland et al., 2020). The general model was formed by abstracting from and integrating the four previous models. Regarding integration, the common components identified above were all included in the overall model (this concerns the subjective interpretation of disease and treatment-related stimuli leading to the experience of illness stressors, cognitive and behavioural responses in reaction to illness stressors, and individual factors that influence the adjustment process). To this were added essential components mentioned only in a few previous models (this concerns in particular emotional and physiological responses in response to the illness stressors, and social and environmental background factors influencing the adjustment process). Regarding abstracting from previous models, a priori assumptions about the interrelationships among cognitive, emotional, behavioural and physiological response systems were avoided in the general model. It was also avoided to focus on a particular mechanism underlying the process of adjustment to disease and treatment. Similarly, the general model was made up of main components, without going into possible sub-subcomponents. The general model proposed here is represented schematically in Figure 5. The model posits that disease and related treatment induce illness stressors, which encompass the subjective experience of acute events and ongoing situations related to disease and treatment (e.g., becoming aware of a disease diagnosis, uncertainty about the future). Illness stressors in turn induce cognitive, emotional, behavioural and physiological responses that influence health outcomes. Examples include catastrophizing thoughts (cognitive response), depressive symptoms (emotional response), avoidance of activity (behavioural response) and dysregulation of the hypothalamic-pituitary-adrenal axis (physiological response). The various cognitive, emotional, behavioural and physiological responses are loosely coupled, parallel systems that do not occur in a specific temporal sequence, but are conceptualised as parallel and interacting systems. Schematic representation of the general model on adjustment to disease and treatment. Background factors influence the experience of illness stressors, as well as the cognitive, emotional, behavioural and physiological responses to these stressors. These factors include the patient's personal background (e.g., personality, life goals) as well as social and environmental background (that is, the context into which the person is embedded, e.g., socio-economic status, neighbourhood). Cognitive, emotional, behavioural and physiological responses affect health, defined as a number of health domains by the World Health Organization (World Health Organization, 2001). Drawing on a proposal to more explicitly articulate psychological processes in this classification (Dekker & de Groot, 2018), the following health domains can be distinguished: (i) disorder or disease, (ii) somatic and mental functions and structures, (iii) activities and participation, (iv) social and environmental factors, and (v) personal factors (Dekker et al., 2023). It should be noted that disease and related stressors can be both an antecedent (cause) and a consequence (effect) in the adjustment process. For example, disease-related pain is a stressor, anteceding cognitive, emotional, behavioural and physiological responses. These responses modulate the pain experience, with a consequent improvement or worsening of pain. To avoid an overly complex figure, these feedback loops have not been visualised in Figure 5. Instead, the figure refers to Time 1 and Time 2. Disease and related stressors are antecedents at Time 1, leading to health outcomes at Time 2. The health outcomes at Time 2 can start a new adjustment process cycle, leading to health outcomes at Time 3, and so on. Earlier versions of this model have been presented elsewhere (Dekker, (in press); Dekker & de Groot, 2018). These publications described an integrated model based on three (Dekker & de Groot, 2018) and then four (Dekker, (in press)) of the previous models mentioned above, and used that integrated model for these publications' specific purposes. The purpose of these publications was not to describe the development of the integrated model. In contrast, the purpose of the present paper is to describe the development of the integrated, general model and how it was derived from the four previous models. In addition, the present paper clarifies the conceptualisation of health as the outcome of the adjustment process, and it addresses the issue that disease and related stressors can be both an antecedent (cause) and a consequence (effect) in the adjustment process. The present paper describes the actual development of the general model, in its final form. Compared to previous models, this general model offers significant added value. First, the general model includes all components of the psychological adjustment process. Several previous models did not include the physiological component, despite the substantial influence on health of psychophysiological responses to stressors. Furthermore, personal background (e.g. (Schreuer et al., 2006)) or social and environmental background (e.g., (Naus et al., 2009)) tended to be ignored in (variants of) the four main models described above. By including all components, the general model is truly comprehensive and has great educational value. Second, a comprehensive general model has both a heuristic function as well as an interpretative function (Dekker, 2008). Regarding the heuristic function, the general model can help direct the development of specific theories and research questions. In other words, which components should be considered to further explain psychological adjustment to disease and treatment? As a practical example, in a recent extension of the common-sense model cognitive responses were emphasised, while emotional responses were viewed almost exclusively as moderators (Hagger & Orbell, 2022). Although an expansion of the original model is welcome, the direct effects of emotions deserve greater emphasis, as do physiological responses, which were not mentioned at all. Moving to the interpretative function: the general model facilitates the interpretation and integration of research findings. How do specific research findings feature in the process of adjustment? For example, a multiple sclerosis self-management model was developed de novo without reference to previous models or research findings (Ghahari et al., 2019). How this rather idiosyncratic multiple sclerosis model relates to previous conceptualisations and research findings could be clarified by mapping it onto the general model. Third, the general model views cognitive, emotional, behavioural and physiological responses as loosely coupled systems. These response systems operate in parallel and can interact, without assuming a priori cause-and-effect relationships. For example, cognitive responses may precede emotional responses (Lazarus & Folkman, 1984), cognitive and emotional responses may act in parallel (Leventhal et al., 1992), or emotional responses may precede cognitive responses (Moss-Morris, 2013). In this respect, the general model resides at a meta-level and avoids a priori assumptions about the interrelationships among response systems. These interrelationships can be articulated in more focused theories for subsequent empirical testing. Fourth, the general model abstracts from previous models, providing a description of the components of the adjustment process and their interrelationships, but avoiding a focus on any particular underlying mechanism. Again, the general model resides at a meta-level in this respect: specific mechanisms such as survival (Lazarus & Folkman, 1984), self-regulation (Leventhal et al., 1992), homeostasis (Moss-Morris, 2013), or allostasis (McEwen, 1998) can be articulated in more focused theories and subsequently empirically tested. Similarly, the general model does not address subcategories within components or variants of the four previous models: these subcategories and variants can be studied in more focused models. The general model covers the four models, their variants and subcategories in components. Fifth, health has been defined as 'the ability to adapt and to self-manage' (Huber et al., 2011). While a focus on adaptation/adjustment and self-management is to be commended, this definition confuses the process of adjustment with its outcome, that is, health. By contrast, the general model distinguishes between the process of adjustment and the outcome health, with health defined in terms of WHO health domains (World Health Organization, 2001) (see above). For example, by providing good health information after a cardiac event an individual can implement lifestyle improvements (process), leading to better physical fitness and prevention of another cardiac event (outcome). The general model makes a straightforward distinction between the process of adjustment and its outcome, viz. health. By abstracting from and integrating previous models, the general model provides a comprehensive conceptualisation of adjustment to disease and treatment. It presents a clear overview of all components of the process of adjustment and their interrelationships, which has great educational value. Furthermore, the general model has scientific value: it has both a heuristic function (guiding the further development of specific theories and research questions) and an interpretive function (facilitating the interpretation and integration of research findings). No specific funding. The author has no conflict of interest to disclose. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.