To the best of our knowledge, this work is the first study to explore the concept of illness identity within a large and representative sample of ACHD at the German Heart Center Munich. Although prior research has addressed the topic of identity within the context of chronic disease management [
13,
14,
25], systematic research on possible antecedents and effects of illness identity in ACHD patients remains insufficient [
11]. The purpose of this study was to conceptualize and measure the relationship between illness identity and emotional distress in terms of anxiety and depression. Current results point towards elevated depressive and anxiety symptoms in ACHD. In contrast to previous studies on ACHD, various clinical variables, such as disease complexity, functional status, cyanosis and surgery status, were considered to account for the true severity status of the patients. Findings appeared to be robust when including various confounding factors, such as sociodemographic and clinical parameters. The present study provides evidence that the IIQ/IIQD is a reliable tool to understand and eventually predict the psychological impact of disease to ACHD patients. Illness identity may play a key role in regulating the amount of emotional distress arising in ACHD. Consequently, a patient’s illness identity may potentially predict psychological functioning and ultimately physiological outcomes in ACHD.
4.3. Objective 3: Associations Between Illness Identity and Emotional Distress
Generally, the present results indicate that the majority of ACHD were able to accept their illness. Since most patients were recruited in the outpatient department, they are probably able to successfully master their everyday lives and engage in their adult responsibilities [
11,
26]. This situation also explains why most patients had a lower functional status in the current sample. However, patients presented heightened scores of depressive and anxiety symptoms. Hence, present findings confirm the current state of research on the increased prevalence of emotional distress in ACHD [
5]. Although patients may function well in day-to-day life, their unrecognized emotional distress may have detrimental effects upon their cardiovascular health. The under-diagnosis of mental health issues and a lack of psychosocial support for ACHD have become increasingly recognized [
27]. There are different reasons for this variance. First, clinicians may place their primary focus on the medical treatment of CHD, and might not be aware that patients experience significant psychological problems. On the other side, patients themselves might be unaware of their emotional symptoms, and might not bring their concerns to clinicians’ attention [
28]. Further, specialized mental health professionals in the field of CHD are still lacking, since psycho-cardiology in ACHD is a young scientific discipline [
29].
Clinically-relevant relations between illness identity and emotional functioning were observed consistent with prior expectations. Accordingly, dysfunctional illness identity states were associated with higher emotional distress, while functional illness identity states correlated with better psychological functioning. While no associations could be observed between disease severity and psychological functioning, illness identity accounted for unique differences in psychological functioning, regardless of the underlying disease severity. Hence, disease severity was associated with illness identity, which in turn influenced psychological functioning in ACHD. Closer inspection of the relations between the four illness identity states and their psychological outcomes revealed that engulfment significantly predicted depression and anxiety in ACHD. Patients who are consumed by their illness may probably experience more limitations in daily functions and greater concern in general [
11]. Evidence suggests that depression leads to increased threat appraisals [
8], which explains the common comorbidity with anxiety [
10,
28].
While health-related anxiety can be beneficial by promoting health awareness and treatment adherence, extreme heart-focused anxiety might further elicit feelings of engulfment and create a vicious cycle of worry and fear [
30]. The constellation of depression and anxiety in engulfed patients is especially alarming, because additive effects with a three-fold increased risk of all-cause mortality have been documented elsewhere [
9]. Rejection was significantly associated with increased anxiety, but unrelated to depression. Present findings indicate though that adverse effects of rejection on psychological functioning were less evident than adverse effects of engulfment. This form of illness integration might be used by patients who perceive their illness as a threat to their identity, and try to escape the stresses of CHD by suppression, denial or self-distraction [
13]. This perception may be initially helpful to temporarily adjust, but long-term effects may prevent patients from applying problem-focused coping strategies [
31]. It has been shown that rejection and fear mutually interact: by avoiding confrontation, the perceived threat increases, which in turn leads to greater fear and more rejection [
32,
33]. Over time, avoidance is known to be associated with continued emotional distress, increased noncompliance to medical regimens, and worse health outcomes [
34,
35]. In this study, acceptance and enrichment were linked to less depressive symptoms, while the magnitude of effect was higher in enrichment. In line with previous findings, individuals who integrate their illness as an integral part of self might take a more active role in their health management, and have a higher sense of controllability. Controllability is considered a critical component in chronic disease management [
36]. It is, therefore, comprehensible that adaptive illness integration is linked to lower depression [
11]. In fact, “acceptance” and “meaning making” are listed as key processes within the framework of self-management in chronic illness [
15]. It is remarkable that both dimensions of adaptive illness integration are unrelated to anxiety. This lack of relationship indicates that anxiety has a two-fold effect when adapting to a chronic illness: While excessive anxiety, as can be found in maladaptive illness identity states, negatively impacts cardiac outcomes and psychological functioning, healthy levels of anxiety might be a prerequisite for properly integrating the illness and taking appropriate steps in monitoring the illness [
37].
Current results should be interpreted with caution due to certain limitations. First, the study was cross-sectional in nature, which does not allow any conclusions about the directionality of effects. It remains to be clarified if illness identity is dynamic in nature or divided into four fixed states ad infinitum. However, illness identity may rather be subject to changes in disease progression and severity, eventual health declines and symptomatic vs. asymptomatic periods [
38]. To clarify the role of illness identity within a dynamic process, longitudinal research of the psychological variables applied in this study is needed. Second, all questionnaires used in this study were based on self-report answers. Obtained results were, therefore, susceptible to response bias. This bias was minimized by assuring patients that the survey was strictly pseudonymized, and responses were not shared with their treatment providers. Third, since all patients were aware of being part of a behavioral study, this awareness might have led to biased responses known as the Hawthorne Effect [
39]. Fourth, methodological limitations need to be noted. The validation of the IIQD has shown that the four dimensions of illness identity are not sufficient to fully cover a patient’s illness experience. In the future, it may be necessary to adapt the IIQ/IIQD and further differentiate the rejection dimension. Fourth, little is known about the relation of illness identity to other psychologically relevant concepts in chronic disease management, such as psychological coping. Coping in the context of heart disease is typically defined according to the Lazarus and Folkman stress and coping paradigm [
40]. Lazarus and Folkman suggest two types of coping: emotion-focused coping involves different ways of emotionally handling the illness in order to reduce emotional distress including wishful thinking, denying, diverting attention or accepting. In contrast, problem-focused strategies directly target the source of stress by activating resources, such as active information seeking and medical compliance. [
40] From this perspective, illness identity would rather belong to emotion-focused coping, as it places the focus on intrapsychic processes of illness integration.
Within this framework, behavioral efforts to handle the illness are regarded as consequences of illness identity, and specific relations between illness identity and practical coping styles still need to be revealed to attain a more nuanced understanding of ACHD and eventually establish psychotherapeutic guidelines.