Interface of resilience with other related concepts in physiological and psychosocial/spiritual domains.

In the health sciences, the term ‘resilience’ is used to refer to the ability to respond to a wide range of challenges, from cellular responses to a stressor such as oxidative stress, to responses to stressful life events such as the death of a family member. As such, the concept of resilience is related to, and partially overlaps with, a variety of other concepts such as homoeostasis (physiological) and post-traumatic growth (psychospiritual). The National Institutes of Health (NIH) Trans-NIH Resilience Working Group defines resilience as the ability to resist, recover, adapt, or grow from a challenge. It is important to examine how this definition of resilience relates to other related concepts across these four domains. In this paper, we discuss examples of resisting, recovering, adapting, and growing in response to a challenge in both physiological and psychological contexts, using examples from SARS-CoV-2 infection and the COVID-19 pandemic, with the main goal of illustrating the broad applicability of the term resilience, as well as its subcategories, across frames of reference. This paper will not discuss resilience and related concepts in disciplines outside the health sciences, such as engineering and ecology. In the physiological domain, resistance to a challenge is exemplified by an asymptomatic viral infection. As demonstrated vividly in the context of the COVID-19 pandemic, some individuals exposed to the SARS-CoV-2 virus generate an immune response that eliminates the virus, as well as creates (or reinforces) immune memory of the pathogen, without producing symptoms. This type of ‘competent’ immune response, using variable combinations of innate and adaptive immunity, allows the individual to resist the challenge posed by the virus and is characterized by both sufficient activation, to eliminate the pathogen, and control and resolution of the immune response when no longer needed (Carsetti et al., 2020). In other words, the physiological response needs to be ‘just enough’ to take care of the problem, and no more. This type of response is related to the general concept of homoeostasis that preserves vital functions (e.g., blood pressure, core temperature) in the presence of transient environmental perturbations and allows the individual to continue functioning normally while the disturbance is present, returning the organism to its baseline state once the challenge is over (Goldstein, 2019). In the psychosocial/spiritual domain, resisting a challenge may involve mental and emotional stability and stamina in a stressful situation, such as social isolation, especially the severe isolation that occurred in the early phase of the COVID pandemic. Fear of contracting COVID is another stressful situation that had an impact on cognition, emotion, and mental health in general (Quadros et al., 2021). The concepts of equanimity and self-efficacy are related to the ability to resist stress; equanimity describing an ability to stay calm in difficult situations, and self-efficacy reflecting confidence in the ability to exert control over one's own motivations, behaviour, and social environment (Mann & Walker, 2022; Peñacoba et al., 2021; Quadros et al., 2021). Physiologically, recovering from a challenge, in contrast to resisting, implies that some amount of disturbance beyond homoeostasis took place, followed by a recovery process. Following up on the previous SARS-CoV-2 infection example, an individual may experience several days of fever, respiratory, and other symptoms, indicating that the virus, temporarily, was able to establish a foothold in the body, multiply, and invade various tissues. Subsequent full resolution of the infection and restoration of health has two components: first, that a robust immune response is able to effectively clear the virus; and second, that immune responses are able to come back to baseline without exaggerated inflammatory manifestations. Resolution of inflammation is now understood to be an integral component of inflammation itself and is an important component of restoration, regeneration, and tissue repair (Andreakos et al., 2021). The concepts of repair and restoration are relevant to the physiological recovery process in a variety of clinical settings. Notably, the role of inflammation is being re-examined in light of our evolving understanding of its role in the repair process (Cooke, 2019). For a systemic illness, recovery often includes a ‘convalescence’ period when the illness itself is no longer present but full health is not yet restored. Although residual fatigue is common in this situation, it is often assumed that once the infection is over, health has been restored. However, in some cases, the convalescence period is marked by setbacks with return of symptoms, and delayed restoration of baseline stamina. In such a case, resilience may also have a behavioural component, such that an individual is able to match his/her return to physical activity to the recovery process. This type of process may play an important adaptive role in recovery from post-acute sequelae of COVID-19 (PASC) (Proal & VanElzakker, 2021). As in the physiological examples, recovering from a psychological challenge also implies that some significantly disruptive trauma has taken place, for example, death of a family member or loss of employment, which many individuals experienced during the COVID-19 pandemic. Successful recovery means that the individual is able to go through a grieving process including varying amounts of denial, sadness, and anger, leading to acceptance of new life circumstances (Maciejewski et al., 2007). Adjusting to the ‘new normal’ post COVID pandemic is an example of complex adaptive processes that may be needed to recover from a societal challenge (Corpuz, 2021). Grief work often transcends the psychological domain and involves spiritual and social components (Walsh, 2020). After the death of a loved one the pain may lessen in intensity over time, but the sadness may never go away. Acceptance describes the process where the individual accepts what has happened and begins to move on in a new reality. Acceptance involves understanding that things will not ever go back to the way they used to be and learning to accept a new normal. In contrast to full recovery, partial recovery implies that, while recovery is not complete and some degree of persistent deficit remains, a lasting positive response to the stressor has taken place. For example, someone recovering from a stroke may be left with a permanent sensory/motor deficit but may have recovered function to the point of being able to perform activities of independent daily living, thus demonstrating resilience. In the case of Long COVID, an individual may experience persistent loss of smell and/or taste, increased fatigue, or sleep disturbance, that may recover to some degree, but not completely (Mantovani et al., 2022). Although there is insufficient data available to understand responses to PASC that may confer resilience, lessons can be drawn from other examples, such as the allostatic response to chronic stress, which we now recognize to have positive and negative components (McEwen, 2007). While flattening of the cortisol rhythm, which occurs with chronic stress, preserves function in the short term (Joseph & Golden, 2017), this comes at the cost of reduced circadian complexity, with physiological consequences that are just beginning to be understood (Nollet et al., 2020). Another concept relevant to partial recovery in the context of immune responses is tolerance, in which an individual may tolerate the ongoing presence of a pathogen while minimizing inflammatory responses that may be more detrimental to the organism than the presence of the pathogen itself (Bergstrom et al., 2012). A concept that bridges the psychological and physical domains is stress-resilience, which specifically addresses built-in neuroendocrine responses including hypothalamic-pituitary-adrenal axis and mesolimbic dopaminergic pathways in response to acute or chronic stress (Cathomas et al., 2019). In the psychosocial/spiritual domain, coping can be defined as ‘cognitive and behavioural efforts to master, reduce, or tolerate the internal and/or external demands that are created by the stressful situation’ (Folkman, 1984). Coping can be positive when it leads to beneficial outcomes in situations that are both taxing and important to the affected individual (e.g., religious coping), or negative when it leads to detrimental or compensatory outcomes (Garfin, 2020; Kar et al., 2021). In the context of the COVID-19 pandemic, the literature appears to show mixed outcomes, with some groups exhibiting substantial negative impacts (i.e., healthcare workers and children/adolescents) whereas other groups appear much less vulnerable to potential psychological impacts of the pandemic (Manchia et al., 2022). Some types of allostatic responses to stress can be thought of as salutogenic if they involve a physiological growth that increases the overall state of health of the individual. The adage ‘what does not kill you makes you stronger’ is a popular expression of the term hormesis, defined as the adaptive response of cells and organisms to mild or moderate stressors that protects from future stressors and may improve the physiological state of the organism (e.g., telomere stabilization, increased mitochondrial energy production) (Epel, 2020). B-cell and T-cell responses to a viral infection, such as SARS-CoV-2, are examples of lasting immunity, which can be thought of as physiological growth in response to the challenge (Rodda et al., 2021). In the psychosocial/spiritual domain, an example of post-traumatic growth is increased positive outlook and appreciation for life after a severe illness, such as hospitalization for SARS-CoV-2. It has been long realized in palliative care and other disciplines that there are some seriously ill or terminal patients who progress beyond the experiences of psychological trauma, coping, and acceptance. Such patients can feel changed for the better or stronger mentally compared to their status before their disease was diagnosed. This phenomenon of ending up stronger mentally than before the onset of illness has been called ‘healing’ in palliative care. A qualitative study with cancer survivors found that some report positive subjective changes described as life transforming. In order to actualize their hopes for improvement these individuals used a self-guided process centred on researching options, gaining experience, and evaluating results. Many of these individuals discovered unanticipated personal resources and abilities which became highly useful in not only coping with the cancer but with other problems in their lives (Skeath et al., 2013). In related disciplines, similar phenomena are known by various names, such as thriving (Carver, 1998; Oleary & Ickovics, 1995) and many other terms. The identifying characteristic is that in relation to a substantially adverse event, the individual feels they have become ‘better than before’ as a person in some important way. Several studies have measured the constructs of healing and post-traumatic growth (Ameli et al., 2018; Despotes et al., 2017; Lowe et al., 2020; Tedeschi et al., 2017; Weir, 2020). In a study of patients with cancer who reported positive life transforming changes it was found that spirituality helped these individuals find increased meaning and purpose. An important part of this spirituality was increased connections to a higher power, other people, their work, the arts, music, and or nature (Young et al., 2015). In elderly African American elders with serious illness, faith in God helped with both the current illness as well as other life difficulties (Coats et al., 2017). A tool, the NIH HEALS has been validated to measure this phenomenon of psychosocial spiritual healing. The main factors related to healing include connection, reflection, introspection, trust and acceptance (Ameli et al., 2018). In the context of human health, resilience and its subcategories can apply equally well to both the psychological and physiological ability to resist, recover, adapt, or grow from a challenge. Indeed, the increasing attention being paid to the concept of resilience across a variety of reference frames attests to the fundamental nature of systems and stressors. Stressors are ubiquitous and a systems response to stressors can take a variety of forms, some of which result in failure and some in resistance, recovery, adaptation, or growth. The authors would like to acknowledge Dr. LaVerne Brown, Dr. Rebecca Costello and Dr. Barbara Cohen for their valuable input on this manuscript. None of the authors have any conflict of interest to share. No data was collected or analysed for this manuscript.