Abstract
There is growing awareness of the role of allostatic load (the cost of chronic exposure to fluctuating or heightened physiologic responses resulting from repeated or chronic stress) in the balance between health and disease. When environmental challenges exceed the individual ability to cope, allostatic overload ensues. The determination of allostatic load initially relied on measurements of biomarkers, and then it was expanded to clinimetric criteria for allostatic overload. It provides a characterization of the individual psychosocial environment that is missing from current clinical diagnostic formulations and has major implications for identifying syndromes that are not included in traditional diagnostic classifications. Healthy lifestyle behavior and euthymia may modulate the vulnerabilities induced by allostatic overload. Here, we present a staging system for the longitudinal development of allostatic load. Consideration of allostatic load allows clinicians to create individually tailored interventions to prevent or decrease the negative impact of environmental factors on health.
In 1960, in a landmark publication that introduced the psychosomatic approach to health and disease, George Engel formulated a broad description of what constitutes psychological stress as
all processes, whether originating in the external environment or within a person, which impose a demand or requirement upon the organism, the resolution or handling of which necessitates work or activity of the mental apparatus before any other system is involved or activated. (Engel, 1960, p. 480)
Engel (1960) anticipated what McEwen and Stellar (1993) defined as allostatic load, which describes the relationship between stress and the processes leading to disease. Their conceptual framework was based on allostasis, the ability of the organism to achieve stability through change (Sterling, 2012). Allostasis complements homeostasis, the goal of which is to preserve constancy of the internal milieu by negative feedback regulatory mechanisms. Allostasis suggests that efficient regulation requires anticipating needs and preparing to satisfy them before they arise. It identifies the brain as the fundamental organ for predictive regulation of the internal milieu (Schulkin & Sterling, 2019; Sterling, 2012). Accordingly, allostatic load is the cost of chronic exposure to fluctuating or heightened neural or neuroendocrine responses resulting from repeated or chronic environmental challenges that an individual reacts to as being particularly stressful (McEwen & Stellar, 1993). It refers to the long-term effects of the wear and tear that result from either too much stress or from inefficient management of allostasis (McEwen & Stellar, 1993). When environmental challenges exceed the individual’s ability to cope, allostatic overload may ensue (McEwen, 2007). As a result of experiences that lead to allostasis and adaptation, but also to allostatic load and overload, the brain is changing its circuitry and function epigenetically (McEwen et al., 2015, 2016).
Situations that may lead to the development of allostatic load or overload are (a) exposure to frequent stressors, which may determine a status of chronic stress and repeated physiological arousal; (b) lack of adaptation to repeated stressors; (c) inability to shut off the stress response after a stressor is terminated; and (d) allostatic response not sufficient to deal with the stressor (McEwen, 1998, 2007).
The introduction of the concept of allostatic load sparked an increasing amount of research geared to the use of biological markers for its identification, as summarized in a recent systematic review (Guidi et al., 2021). The findings indicated that higher allostatic load was associated with poorer health outcomes in both general and clinical populations. The biological model of allostatic load focuses on glucocorticoid dysregulation as part of a network of mediators involving autonomic, endocrine, metabolic, and inflammatory parameters (McEwen & Stellar, 1993; Seeman et al., 2001). It has been expressed in cumulative indexes encompassing clinical and laboratory parameters (Buckwalter et al., 2016; Seeman et al., 2001). This line of research on allostatic load relies on biomarkers that express a state of body systems but does not provide information on the underlying individual causes. Moreover, substantial heterogeneity exists across studies as to the type and number of parameters to be considered (Liu et al., 2021; Whelan et al., 2021).
In this article, allostasis refers to the ability of the organism to achieve stability through change (Sterling, 2012), allostatic load is applied to the cumulative effects of stressful experiences in daily life (McEwen & Stellar, 1993), and allostatic overload refers to the presence of stressors exceeding individual coping skills according to specific criteria (Fava et al., 2019). The purpose of this article is to review the clinical meaning and implications of allostatic load, with special reference to its clinimetric assessment and practical applications in everyday practice.
The Clinical Meaning of Allostatic Load
A large part of psychosomatic research on the relationship between stress and illness has been concerned with life events (Fava & Sonino, 2010). The term life events refers to discrete changes in the subject’s social or personal environment that should be external and verifiable rather than internal or psychological. Research methodology initially relied on self-rated retrospective collection of life events included in a list, such as in Holmes and Rahe’s (1968) Social Readjustment Rating Scale (SRRS). Because each life event had a score based on the mean level of adaptation that the average subject in the population would require for coping with the change (Holmes & Rahe, 1968), individual scores could be compared among populations retrospectively and could be used to establish the general degree of vulnerability to illness in prospective studies. This approach, however, had limited success and was liable to considerable methodological shortcomings (Theorell, 2012). Subsequent methodological approaches based on detailed interviewing and with structured methods of data collection and control groups have allowed researchers to substantiate the link between life events in the year preceding the onset of symptoms and a number of medical disorders, encompassing endocrine, cardiovascular, respiratory, gastrointestinal, dermatological, autoimmune, and neoplastic disease (Fava, Cosci, & Sonino, 2017; Fava & Sonino, 2010; Theorell, 2012). However, the methodology of life events collection acknowledged the need for placing events into a context (Theorell, 2012). For instance, Paykel’s Interview for Recent Life Events points to the objective negative impact of the event (the rater makes a judgment of the expected stressfulness of the event when its full nature and particular circumstances are taken into account, ignoring the subjective reaction of the individual; Paykel, 1997; Sonino, Fava, & Boscaro, 1993; Sonino, Girelli, et al., 1993). McEwen and Stellar’s (1993) definition of allostatic load synthesized the cumulative effects of experiences in daily life that involve both ordinary events as well as major challenges generally subsumed under the rubric of life events. Indeed, subtle and long-standing life situations should not be too readily dismissed as minor or negligible because chronic, daily life stresses may be experienced by the individual as taxing or exceeding his or her coping skills (Wagner, 1990). The conceptual framework of allostatic load was also extended to work, unemployment, adverse living conditions, social and educational experiences, and income inequality throughout life-span development (Juster et al., 2011; McEwen, 1998, 2007; McEwen & Stellar, 1993). Moreover, adverse experiences in childhood were found to predict high levels of allostatic load later in life (Agorastos et al., 2019; Danese & McEwen, 2012). General population studies indicate that allostatic load is increased by low socioeconomic status, living in impoverished neighborhoods, low educational attainment, and ethnicity and racial discrimination (Guidi et al., 2021). This comprehensive model also included the physiological consequences of the resulting health-damaging behaviors, such as poor sleep and other aspects of circadian disruption, poor diet, smoking, alcohol consumption, and social isolation (Guidi et al., 2021; McEwen, 1998, 2007; McEwen & Stellar, 1993).
However, the clinical richness of this approach, which reflects the breadth of McEwen’s interdisciplinary work and commitment to social justice (Horwitz et al., 2021), for a long time did not produce clinical methodologies that could be used in everyday practice. Help in assessing a state of allostatic load came from clinimetrics, the science of clinical measurements (Carrozzino et al., 2021; Fava et al., 2018; Fava, Tomba, & Sonino, 2012; Feinstein, 1982, 1987), a domain concerned with indices, rating scales, and other expressions that are used to describe or measure symptoms, physical signs, and other clinical phenomena that are not found in the customary taxonomy. For a long time, development of assessment tools was based on psychometric principles, but this had two major drawbacks (Fava et al., 2018). One is the psychometric assumption of the need for homogeneity of components of rating scales, as measured by statistical tests such as Cronbach’s alpha and factorial analysis. This is in contrast with the fact that in clinical medicine, patients express symptoms that are highly heterogeneous (Fava, Tomba, & Sonino, 2012). The redundant components that create a high scale score for homogeneity are likely to obscure its capacity to record changes in clinical status. Further, in classical psychometrics, all items of a rating scale have the same weight and measure parallel forms of the same symptom (Feinstein, 1987). Yet in clinical practice (as reflected by the clinimetric approach), not all symptoms have the same weight (major and minor symptoms can be differentiated, such as in Jones’ criteria for rheumatic fever; Feinstein, 1982). In the clinimetric approach, neither homogeneity of components nor unidimensionality are required, in line with the heterogeneous features of clinical variables (Carrozzino et al., 2021; Fava et al., 2018; Fava, Tomba, & Sonino, 2012). What matters is the clinical utility and sensitivity of a scale (the capacity to discriminate between active treatment and placebo, to differentiate between groups of patients, and to capture changes in clinical status).
The Clinimetric Model of Allostatic Load
A first step into the clinimetric assessment of allostatic load was the development of the Psychosocial Index (PSI; Piolanti et al., 2016; Sonino & Fava, 1998). This is a short, self-rated questionnaire, tailored to busy clinical settings, for the assessment of stress and related psychological distress (allostatic load) and fulfills the clinimetric criteria for patient-reported outcome measures (Carrozzino et al., 2021). It includes 55 items, mostly derived from previously validated instruments. Thirty-five items were selected from Kellner’s Screening List for Psychosocial Problems (SLP; Kellner, 1991) after eliminating all sources of redundancy. They constitute the sociodemographic and clinical data section, the psychological distress scale, and part of the stress scale. The latter has been integrated with 10 items derived from the Wheatley Stress Profile (WSP; Wheatley, 1990). Six questions were derived from Ryff’s Psychological Well-Being (PWB) scales (Ryff, 2014) and contribute to the well-being scale. Three additional questions were selected from Kellner’s Illness Attitude Scales (IAS; Sirri et al., 2008) and address abnormal illness behavior.
The PSI covers six domains. The first is sociodemographic and clinical data, which encompasses routine information about medical and psychiatric history, the patient’s family, employment and habits; it may alert clinicians to some threats to health, such as alcohol or drug use. The second domain is stress, which integrates both perceived and objective stress, life events, and chronic stress, with particular reference to work (or lack of it) and home environment. These questions contain essential information for case identification of allostatic overload, including impairment in occupational/social functioning (Items 21–26). The third domain is psychological distress, which consists of a checklist of symptoms addressing sleep disturbances, somatization, anxiety, depression, and irritability. Three questions refer to sleep disturbances and may also be scored separately from the other questions. The fourth domain is abnormal illness behavior, which allows the assessment of hypochondriacal beliefs and bodily preoccupations (Fava, Cosci, & Sonino, 2017). The fifth domain is well-being, which covers areas such as environmental mastery (Items 33 and 34) and positive relations with other people (Items 31 and 32). Impaired environmental mastery may indicate that the person feels difficulties in managing everyday affairs, feels unable to improve things around them, or is unaware of opportunities (Fava & Guidi, 2020; Guidi & Fava, 2021). Positive interpersonal relationships (i.e., the person has trusting relationships with other people, is concerned about the welfare of others, and understands the give and take of human relationships) are an important mediating factor for the impact of situations (Theorell, 2012). The final domain is quality of life. A simple direct question on quality of life (Item 55) is included, following Gill and Feinstein’s (1994) recommendation.
The PSI (Piolanti et al., 2016; Sonino & Fava, 1998) can be used as a self-rating scale or as an observer-rated measure (the clinician, by scanning the patient’s responses, can rate the dimensions of stress and allostatic load, psychological distress, abnormal illness behavior, and well-being). PSI scores have been used in psycho-endocrine studies (Sonino et al., 2007, 2011) and have been found to yield a sensitive assessment of allostatic load across different patient subgroups. Table 1 lists the studies in which allostatic overload was identified on the basis of information gathered through the PSI (Eöry et al., 2021; Gostoli et al., 2016; Offidani et al., 2013; Peng et al., 2021; Ruini et al., 2015), according to specific algorithms.
Prevalence of Allostatic Overload Based on Information Gathered by the Self-Rated Psychosocial Index
The Definition of Allostatic Overload
The normal allostatic response is initiated by a stressor, sustained for a given interval, and then turned off (McEwen, 2007). McEwen and Wingfield (2010) defined allostatic overload as the transition to an extreme state. However, it is not easy to distinguish the threshold between tolerable stress (a physiological state that could potentially be disruptive but is buffered by the personal and interpersonal resources of the individual and occurs within a time-limited frame) and toxic stress (strong, frequent, and/or prolonged activation of the body’s stress response system and lack of buffering factors or protection; McEwen & Wingfield, 2010).
Clinimetric criteria for the determination of allostatic overload were introduced in 2010 (Fava et al., 2010). They were subsequently incorporated in the Diagnostic Criteria for Psychosomatic Research (Fava, Cosci, & Sonino, 2017) under a specific diagnostic rubric and supplemented by a semistructured research interview (Fava et al., 2019).
Two criteria are required for the identification of allostatic overload. The first is the presence of a current identifiable source of distress in the form of recent life events and/or chronic stress. The stressor is judged to tax or exceed the individual’s coping skills when its full nature and full circumstances are evaluated. Second, the stressor has to be associated with one or more of the following features, which must have occurred within 6 months after the onset of the stressor: (a) at least two of the following symptoms: difficulty falling asleep, restless sleep, early morning awakening, lack of energy, dizziness, generalized anxiety, irritability, sadness, demoralization; (b) significant impairment in social or occupational functioning; and/or (c) significant impairment in environmental mastery (feeling overwhelmed by the demands of everyday life; Fava et al., 2019).
The semistructured interview for the determination of allostatic overload (Fava et al., 2019), which was developed on the basis of clinimetric criteria, encompasses most of the contents covered by the PSI items (Sonino & Fava, 1998) and may help clinicians formulate a global judgment of an individual’s assets and coping skills in dealing with his or her current life situation.
Table 2 displays the studies in which the presence of allostatic overload was determined through clinical interviews based on clinimetric criteria in medical settings (Cosci et al., 2020; Guidi et al., 2016; Guidi, Lucente, et al., 2020; Leombruni et al., 2019; Piolanti et al., 2019; Porcelli et al., 2012).
Prevalence of Allostatic Overload Assessed by Interviews in Medical Populations
The studies included in Tables 1 and 2 indicate that determination of allostatic overload may be associated with biological parameters, even though a systematic comparison between a comprehensive battery of biomarkers and clinimetric criteria is still missing. Allostatic overload appeared to be related to several other manifestations of psychological distress and impaired well-being in a variety of medical settings.
For a thorough evaluation, an integrated approach that includes both clinimetric criteria and biological markers for the identification of allostatic overload has been recommended (Fava et al., 2019; Guidi et al., 2021). The clinical interview is the primary method for diagnosis. The presence of biomarkers that are consistent with allostatic overload may reinforce the clinical data.
The criteria lend themselves to the configuration of a staging system (Table 3). Staging indicates where a person is in the process of developing a clinical condition (Cosci & Fava, 2013; Fava & Kellner, 1993). Thus, once an index defines the existence of a particular disease state (on the basis of diagnostic criteria), its seriousness, extent, and longitudinal characteristics need to be evaluated. The staging system that is presented in Table 3 starts with a situation in which a person may encounter stressful and demanding situations in everyday life but is able to manage them successfully, a condition that may be subsumed under the definition of euthymia (Stage 0; Fava & Guidi, 2020; Guidi & Fava, 2020). Over months or years, such a burden may exceed the capacities of an individual, be aggravated by life events, and undermine the person’s well-being (Stage 1). The clinical value of the concept of allostatic load compared with classic life-event research is that it takes into consideration the duration of stressors. For instance, caregiving may assume a different connotation depending on whether it extends over a few weeks, months, or years. Worse quality of sleep and the fact that weekends and periods of rest are no longer restorative (and, indeed, individuals may feel worse during those times) are a warning sign of a situation that is deteriorating. The biological components of allostatic load produce a cumulative effect over time, which may or may not manifest in a state of allostatic overload, defined with specific criteria (Stage 2; Fava et al., 2019). Biomarkers are likely to be present. In Stage 3, we may witness the onset of medical and/or psychiatric disorders (e.g., a major depressive episode) or aggravation of an already existing condition, such as Type II diabetes or hypertension (Guidi, Lucente, et al., 2020). The staging system (Table 3) may guide interventions that reverse the progressive worsening of the situation and lends itself to major preventive efforts in high-risk individuals. There are several types of interventions that may run counter to progression in the staging system, such as making the patient aware of the need for decreasing stress exposure, improving sleep quality and diet, increasing physical activity, and counteracting loneliness (Kall et al., 2021; Levi, 1997; Rosenberg et al., 2020; Theorell, 2020b). Interventions include lifestyle medicine (Rippe, 2019) and psychotherapeutic approaches geared to euthymia (Guidi & Fava, 2020).
Staging of Development of Allostatic Load and Overload
A staging model can be validated with longitudinal studies in general and clinical populations, with particular reference to individuals undergoing stressful environmental circumstances (Levi, 1997; Theorell, 2020b). Research strategies addressing the predictive role of individual levels of allostatic load may have important implications both in the general population (e.g., increased illness vulnerability) and in clinical samples (e.g., poor outcome, treatment resistance).
Clinical Applications
A clinimetric evaluation of allostatic load and overload can increase the number of people screened, set the use of biomarkers in a clinical context, and broaden dissemination of measures to prevent or decrease the negative impact of toxic stress on health (Fava et al., 2019). A recent systematic review (Guidi et al., 2021) supports the utility of identifying allostatic load and overload in a variety of clinical situations.
Primary diagnostic configuration of symptomatology
A state of allostatic overload entails several clinical manifestations that can be observed in daily practice. Examples may be provided by worsening of symptoms during weekends or vacation (inability to shut off responses associated with work) or breakdowns that occur just when a stressor has terminated (caregivers of patients successfully recovering after a long struggle; Fava et al., 2019). Such manifestations often do not require medical attention until the individual perceives his or her inability to cope with the surrounding situation or starts experiencing troublesome symptomatology. In a study performed in primary care (Guidi, Piolanti, et al., 2020; Piolanti et al., 2019), allostatic overload was identified in 31 of 200 attendees (15.5%). Of these 31, allostatic overload was associated with a psychiatric disorder in 13 (42%), according to criteria in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association [APA], 2013), whereas in 18 (58%), there was no additional diagnosis. This indicates that the diagnostic criteria for allostatic overload (Fava et al., 2019) may provide the only source of identification of psychological distress in medical patients.
In a system of health care characterized by rigid, artificial boundaries among medical specialties and based mostly on organ systems (e.g., cardiology, gastroenterology), diagnostic labels may simply depend on the location of symptoms. Such labels, however, may fail to identify the underlying state of allostatic overload. Individuals may try to counteract manifestations of allostatic overload by the use of medications (e.g., sleeping pills), yet medications are unlikely to solve their problems. Often, people may attempt to overcome manifestations of allostatic overload by unhealthy behaviors (e.g., alcohol consumption). A timely recognition of a state of allostatic overload is thus of primary importance. We should expect and look for it among people in work situations that are particularly burdensome (Theorell, 2012), such as in medical personnel during the COVID-19 pandemic (Cao et al., 2020; Peng et al., 2021; Theorell, 2020a; Zhang et al., 2020).
Incremental value in assessment
Assessment of allostatic overload may help to demarcate substantial clinical differences among patients who otherwise seem deceptively similar because they share the same medical diagnosis, as was found to be the case in cardiovascular diseases (Gillespie et al., 2019; Nelson et al., 2007; Sabbah et al., 2008), particularly congestive heart failure (Guidi et al., 2016), atrial fibrillation (Offidani et al., 2013), and hypertension (Guidi, Lucente, et al., 2020). It may increase the predictive power of the evaluation procedure both in medical and psychiatric patients. In medical patients, the case of functional somatic symptoms that are commonly encountered in clinical practice, and yet fail to receive adequate attention and care (Fava, Guidi, et al., 2012; Henningsen et al., 2018; Kroenke, 2014), is emblematic. There is a strong relationship between stressful life situations and some functional medical disorders, such as neurocirculatory asthenia/atypical chest pain (Sonino et al., 1998). On the basis of clinimetric criteria, a recent preliminary study on female outpatients with fibromyalgia found prevalent allostatic overload in as much as 25% of the sample (Leombruni et al., 2019). If a source of environmental stress is identified, therapeutic measures can have a specific target (Henningsen et al., 2018). Another important area of application has to do with laboratory measurements that may be affected by stressful life situations. For instance, in case of prolactin levels above normal that do not reach the high values of prolactinoma and are associated with a state of allostatic overload, the stress-related meaning of the laboratory result appears to be likely (Sonino et al., 2015).
The evaluation of allostatic overload fills a gap in the current psychiatric classification, DSM-5 (APA, 2013), which lacks any reference to psychosocial and environmental problems. Unlike in the case of adjustment disorders in the DSM-5 (APA, 2013), the presence of a psychiatric disorder is not a source of exclusion from the criteria. There are major conceptual and methodological flaws in the DSM-5’s categorization of adjustment disorders (Bachem & Casey, 2018; Semprini et al., 2010). A major problem is that adjustment disorder is an exclusionary psychiatric diagnosis (it cannot be applied in combination with other psychiatric disorders) that overlaps with subthreshold manifestations of mood and anxiety disorders (Bachem & Casey, 2018; Semprini et al., 2010). Allostatic overload does not have a psychiatric connotation: It is a transdiagnostic psychosocial categorization (Fava et al., 2019) that may be applied with or without psychiatric and/or medical conditions. The requirements for the determination of the stress component are far more stringent and call for a more detailed exploration than those entailed by the stress definition of adjustment disorders (APA, 2013).
Extensive research has substantiated the potential detrimental role of working situations, such as in the case of burnout syndromes (Linden & Arnold, 2021; Peng et al., 2021; Theorell, 2020a), unemployment (Theorell, 2012), poor living conditions, loneliness, and social isolation (Horwitz et al., 2022). Evaluating allostatic load also means paying attention to the social context of the individual.
Monitoring the course of illness
Evaluation of allostatic load plays an important part in the various phases of medical and psychiatric illnesses. After discharge from the hospital, patients face a transient period of general vulnerability to disease as well as an elevated risk for adverse events, including hospital readmission and mortality, which is frequently referred to as posthospital syndrome (Goldwater et al., 2018). Yet this syndrome can also be viewed as a consequence of allostatic overload (sleep disruption, malnourishment and dehydration, mobility restriction, pain, fears, and distress) (Goldwater et al., 2018). Surgery may increase the level of allostatic load and affect convalescence. Long-standing medical disorders may imply a degree of irreversibility of the pathological process and induce highly individualized modalities of response (Fava, Cosci, & Sonino, 2017). Allostatic overload may impair the rehabilitation process, particularly when it is associated with unrealistic expectations of rapid recovery, as was found to be the case after surgery for endocrine disorders (Sonino & Fava, 2012; Sonino et al., 2015; Sonino & Peruzzi, 2009).
In psychiatric disorders, it is important to identify periods of enhanced vulnerability to relapse. For instance, stressful life events have been associated with relapse during maintenance treatment with antidepressant drugs in depression (Paykel & Tanner, 1976). Appraisal of allostatic overload may lead to timely prevention of such episodes (Fava et al., 2019).
Treatment resistance
Treatment outcome is the cumulative result of the interaction of a selected treatment with several classes of variables: living conditions (e.g., housing, nutrition, work environment, social support), patient characteristics (e.g., age, sex, genetics, general health conditions, personality, well-being), illness features, previous therapeutic experience, self-management, treatment setting (e.g., physician’s attitude and attention), and illness behavior (Fava, Guidi, et al., 2017). Such variables may be therapeutic or counter-therapeutic. In certain patients, their interaction may lead to clinical improvement, but in other cases, it may produce no effect or lead to worsening of the condition. Looking for counter-therapeutic factors is an important and yet neglected issue when treatments do not yield expected results or have failed, as may happen in depression (Fava et al., 2020). Allostatic overload may constitute a counter-therapeutic component both in medical and psychiatric patients. For instance, among patients with essential hypertension, 32.5% reported allostatic overload and displayed significantly higher levels of psychological distress and lower levels of well-being and quality of life (Guidi, Lucente, et al., 2020). In this context, lifestyle modifications such as weight loss and physical exercise (Rippe, 2019) may yield adequate control of blood pressure (McEwen, 2017; Sterling, 2012). This has been illustrated in a clinical case (Fava et al., 2019). In psychiatric settings, patients dealing with difficult family, work, and/or financial situations may display a limited response to psychotropic drugs, whereas the clinical situation is likely to improve when, because of psychotherapeutic interventions or better life circumstances, allostatic load decreases (Fava et al., 2020).
Association with lifestyle
Allostatic load has been associated with health-damaging lifestyle habits (Guidi et al., 2021; Juster et al., 2011). Poor sleep quality, an unhealthy diet and being overweight, lack of physical activity, alcohol consumption, and smoking habits were associated with high allostatic load (Guidi et al., 2021). The metabolic syndrome is a consequence of harmful lifestyle, frequently associated with allostatic load (Seeman et al., 2001), and there is a need to prevent its occurrence as early as possible in life (Shonkoff et al., 2009). The experience of allostatic overload may induce or worsen unhealthy habits, such as smoking and alcohol use (Juster et al., 2011). The devastating effects of unhealthy lifestyles in inducing illnesses and the importance of promoting lifestyle modifications are increasingly recognized in clinical medicine (Rippe, 2019). For instance, there is extensive evidence on the relationship between type A behavior and cardiovascular illness and on the benefits that can be obtained through tailored interventions (Cosci, 2012; Rafanelli et al., 2020). Yet stressful life patterns are not as easily acknowledged as a form of health-damaging behavior (Fava et al., 2019).
Relationship with euthymia
Euthymia is a recently developed transdiagnostic construct that refers to lack of mood disturbances, the presence of positive affect and psychological well-being (i.e., balance and integration of psychic forces; flexibility), a unifying outlook on life that guides actions and feelings for shaping the future accordingly (consistency), and resistance to stress (resilience and anxiety/frustration tolerance; Fava & Guidi, 2020; Guidi & Fava, 2022). It requires a clinical assessment based on clinimetric principles that goes beyond current reductionistic and purely symptomatic use of DSM-5 psychiatric criteria (APA, 2013). Unlike previous models related to psychological well-being, which are exclusively focused on the intraindividual level, euthymia results from interacting mechanisms at the individual, interpersonal, and environmental levels. These latter include work, unemployment, adverse living conditions, social and educational experiences, income inequality, stressful life circumstances, racism, and sexism (Guidi & Fava, 2022; Horwitz et al., 2022).
Sterling (2012) remarked that the allostasis model defines health as optimal predictive fluctuation, because increased demand calls for increased response capacity (Sterling, 2012). As McEwen (2020) pointed out,
euthymia means using allostasis optimally and maintaining a healthy balance that promotes positive aspects of brain and body health through health-promoting behaviors. These behaviors involve not only diet, but also adequate and good quality sleep, positive social interactions, as well as a positive physical environment that is safe and includes green space, all of which reduce allostatic load. (p. 58)
However, health promotion entails considerable difficulties in its application (Fava, Cosci, & Sonino, 2017; Rippe, 2019). Lifestyle modification focused on weight reduction, increased physical activity, and healthy diet is advised as first-line therapy for a number of medical disorders, yet psychological distress and low levels of well-being are major obstacles to behavioral changes (Holt, 2019). It has been argued that enduring lifestyle changes can be achieved only with a personalized approach that targets psychological well-being (Guidi & Fava, 2020; Rafanelli et al., 2020). Strategies pointing to euthymia, such as well-being therapy (Fava, 2016; Guidi & Fava, 2021), need to be tested in lifestyle interventions and in the prevention of both physical and mental disorders.
Conclusions
There are major clinical implications of the model of allostatic load, the assessment of which increases the understanding of psychosocial determinants of health (Fava, Cosci, & Sonino, 2017). Although euthymia and coping styles at the individual level may modulate the vulnerabilities induced by allostatic load (Chen et al., 2012; McEwen, 2020), large improvements in health might be achieved by enhancing public life; improving housing, work conditions, environment, contact with nature; and practicing sports (Sterling, 2012), as pioneered by Lennart Levi (1997). Addressing unemployment, which deprives people of personal identity, social contacts, material assets, and meaning of life, may be an important area of intervention (Levi, 1997). Inclusion of allostatic load in the clinical evaluation allows us to view illness in the interaction between the individual and the social environment, including factors that make individuals susceptible to disease, resilient when disease occurs, and variably responsive to treatment (Horwitz et al., 2022).
Assessment of allostatic load and overload should become mandatory in clinical practice. This approach is highly individualized, taking into consideration the effect of the psychosocial environment on the individual, staging the process caused by dysregulated systems through clinical signs, and discussing the modulating effects of healthy behaviors and euthymia. McEwen (2017) has emphasized how coping with daily life challenges is continuously shaping both brain circuitry and systemic physiology, which, in turn, determine lifestyle choices in terms of protective or damaging health behaviors. Consideration of the impact of allostatic load on health also calls for a multidisciplinary organization of health care to overcome the artificial boundaries among medical specialties that appear more and more inadequate in dealing with symptoms and problems that are not necessarily bound to organ system subdivisions (Fava, Cosci, & Sonino, 2017). Consideration of allostatic load, including the staging system depicted in Table 3, allows clinicians to create individually tailored interventions to prevent or decrease the negative impact of environmental factors on health. Assessment of allostatic load in the context of medical and psychiatric diseases provides a characterization of the individual psychosocial environment that is missing from current diagnostic formulations such as the DSM-5 (APA, 2013).
Footnotes
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Action Editor: Vina Goghari
Editor: Jennifer L. Tackett
Author Contributions
