Exploring the bidirectional relationship between myasthenia gravis and psychiatric comorbidities

1. Introduction

Myasthenia gravis (MG) is a chronic autoimmune disease that causes fluctuating weakness and fatigue in voluntary muscles^(1-6). Myasthenia gravis is considered the most prevalent neuromuscular disorder and is an excellent model of the intricate interplay between neuromuscular junction (NMJ) dysfunction and autoantibody-mediated disorders^(7,8). The pathogenesis of MG involves damage to the postsynaptic membrane of the NMJ, which is mainly caused by pathogenic IgG autoantibodies and complement^(2,9,10).

The number of people affected by myasthenia gravis has been increasing worldwide in recent decades^(7,8,11). However, studies have reported varying rates across regions and populations. In Europe, the reported prevalence of MG rates vary from 11.17 to 36.1 per 100,000 persons^(2,12,13), and globally, myasthenia gravis affects approximately 12.4 individuals per 100,000 people^(1,14).

Patients with myasthenia gravis are classified into subgroups based on factors such as clinical presentation, age at onset, autoantibody patterns, and thymus pathology^(1,9,15). These subgroups provide valuable information and help identify differences in epidemiology, underlying disease mechanisms, severity levels, and responses to therapeutic interventions⁽¹⁾.

Serologically, the classic seropositive subgroup is defined by antibodies targeting the muscle acetylcholine receptor (AChR), which are observed in 70-85% of cases and show high specificity^(16-19). Conversely, a smaller proportion of patients, approximately 5% to 6% with seronegative AChR myasthenia gravis, exhibit antibodies against muscle-specific kinase (MuSK). At the same time, lipoprotein receptor-related protein 4 (LRP4) antibodies are found in 2% to 27% of individuals with double-seronegative MG (dSnMG) – where both AChR and MuSK antibodies are absent^(1,17-19). However, some MG patients remain seronegative, lacking detectable antibodies against known antigens^(18,20-22).

From a clinical perspective, patients can be categorized into two groups: exclusively ocular symptoms (around 10-15% of all patients with myasthenia gravis) and those with generalized myasthenia gravis (85-90%)^(1,4,11). Regarding the onset of diseases, three distinct grou­pings can be identified. Individuals who have their initial symptoms before reaching the age of 18 years old are classified as having juvenile-onset myasthenia gravis. Early-onset MG refers to patients who experience symptoms between the ages of 19 and 50. Males are more prevalent among patients with late-onset MG, which occurs after the age of 50 years old⁽¹⁾.

The clinical symptoms in myasthenia gravis typically manifest a diverse clinical spectrum that encompasses presentations ranging from a purely ocular form of MG to more severe manifestations involving weakness in the limbs, bulbar muscles, and respiratory muscles alongside ocular symptoms⁽¹¹⁾. The different ways myasthenia gravis can present itself and the variability of the symptoms show how complex it is and how it can significantly affect a person’s quality of life and ability to function^(23,24).

Patients with ongoing myasthenia gravis may face challenges in maintaining employment due to symptoms such as fatigable weakness and diplopia. These symptoms can limit their ability to work effectively and independently, contributing to feelings of anxiety and reduced well-being^(5,24).

Depression and anxiety are commonly observed in individuals diagnosed with myasthenia gravis; the prevalence of these mental health issues is notably high among MG patients, complicating their overall care and treatment^(25-27). Recognizing and addressing the psychological aspects of myasthenia gravis are essential for holistic patient care, requiring a multidisciplinary approach that integrates medical treatment with psychological support to relieve symptoms and improve overall well-being.

Depression is a common comorbidity in individuals with chronic illnesses such as myasthenia gravis, which makes their medical and psychological management more complex⁽²⁸⁾. The relationship between chronic disease and emotional state is often bidirectional, with each condition frequently exacerbating the other. Chronic illness can significantly impact mood, leading to stress, irritability and feelings of hopelessness, contributing to the development or exacerbation of depressive symptoms. Conversely, depression can exacerbate the chronic illness by undermining the patient’s ability to manage their condition effectively. This creates a detrimental cycle where the patient’s health deteriorates due to neglect, leading to increased feelings of hopelessness and further neglect of treatment. The inability to adhere to treatment regimens can intensify feelings of guilt and self-criticism, exacerbating depression. Addressing depression in the context of chronic illness requires a holistic approach that integrates medical, psychological and social interventions to improve the quality of life in these patients^(29-32).

Despite almost a century of progress in developing effective treatments for the physical symptoms of myasthenia gravis, there still needs to be a greater understanding of the precise connection between this disease and the psychological disorders that are commonly associated with it. While treatments have greatly improved to address the somatic manifestations of myasthenia gravis, there is limited knowledge regarding how MG intersects with psychological conditions. This gap highlights the need for further research to explore the relationship between myasthenia gravis and psychological well-being, ultimately leading to more comprehensive care strategies for individuals living with this complex autoimmune disorder.

The main objective of the study was to investigate possible associations between the progression of myasthenia gravis, depression and anxiety. By analyzing the complex interplay between these conditions and identifying the reciprocal impact of MG progression and mental health status, we aimed to gain a better understanding of the bidirectional causality between myasthenia gravis and psychiatric comorbidities. Additionally, we aimed to evaluate treatment responses in patients presenting with both myasthenia gravis and depression, assessing the effectiveness of therapeutic interventions in addressing MG’s physical and psychological aspects.

2. Materials and method

2.1. Study design and participants

This research was based on data from a study conducted at the Neurology II Department of Myasthenia Gravis, Clinical Institute Fundeni, in Bucharest, Romania, a tertiary care hospital, from January 2019 to December 2020. The study included 122 patients diagnosed with autoimmune myasthenia gravis (MG) who met specific inclusion and exclusion criteria. The cohort included both male and female patients over the age of 18. The patients were divided into two groups: MG w/dep Group, which consisted of 49 myasthenia gravis patients diagnosed with depressive disorder and receiving antidepressant medication, and MG w/o dep Group, which included 73 MG patients without a diagnosis of depression. Our current research focuses on the 49 patients from the MG w/dep Group to investigate the relationship between myasthenia gravis and depressive disorders, as well as the impact of antidepressant treatment on this patients’ population.

To be included in the study, patients had to meet the following criteria: they had to be over 18 years old, to have a confirmed diagnosis of myasthenia gravis, and be diagnosed with a depressive disorder and/or anxiety, based on the Diagnostic and Statistical Manual of Mental Disorders, 5^th Edition (DSM-5).

Myasthenia gravis diagnosis was established based on widely accepted criteria, including typical clinical manifestations and confirmation by at least one specific diagnostic test. These tests included the demonstration of a characteristic decrease in repetitive nerve stimulation or increased agitation on single-fiber electromyography, the observation of a positive response to administering anticholinesterases for muscle weakness, and the detection of MG-specific antibodies. In addition, all MG patients were screened for thymoma using computed tomography (CT) or magnetic resonance imaging (MRI) scans of the mediastinum to identify any associated tumor.

The study’s exclusion criteria included those having a documented history of particular psychiatric diseases as defined by the DSM-5 criteria, such as bipolar disorder, schizophrenia and dementia. Additionally, individuals with a history of drug dependency or use, as per DSM-5 categories, and those diagnosed with corticosteroid-induced psychosis were also excluded. The study excluded participants with missing clinical data and patients who refused to participate or did not offer the informed consent. It should be noted that patients previously diagnosed with depression and/or anxiety were not excluded, nor were those previously receiving antidepressant treatment.

After completing the screening procedures, 49 eligible patients who met the predefined inclusion and exclusion criteria completed both baseline and six-month visits, and were selected for the study cohort.

Before participating in the study, all patients were required to submit the written informed consent after a comprehensive explanation of the study methods, following the Declaration of Helsinki and according to the country’s law. Additionally, measures were taken to ensure their anonymity. The study obtained permission from the ethics committee of the Fundeni Clinical Institute, Bucharest, Romania. IRB number: 57523.

The sociodemographic and clinical data of the patients were collected by thoroughly reviewing electronic medical records and conducting comprehensive clinical interviews.

Patients underwent evaluations at baseline and six months after that. These assessments involved comprehensive clinical evaluations conducted by both a neurologist and a psychiatrist.

The researchers did not influence the treatment choice based on the scales’ results, maintaining the integrity of the subsequent therapeutic approach.

2.2. Assessment instruments

During the process of diagnosing depression, each participant went through a comprehensive evaluation that was carried out by a proficient psychiatrist using a semi-structured interview. Those individuals who met the criteria laid out in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)⁽³³⁾, were either diagnosed or confirmed to have a depressive disorder. The psychiatrist recorded the patients’ compliance with the prescribed antidepressant medication regimen, along with the particular antidepressant allocated to each patient. The antidepressants used for patients with myasthenia gravis and depression included selective serotonin reuptake inhibitors (SSRIs) such as escitalopram and sertraline, selective serotonin and norepinephrine reuptake inhibitors (SNRIs) like duloxetine, and atypical antidepressants such as mirtazapine and trazodone. 

Also, a neurologist performed an assessment to determine the patient’s clinical status, using the Myasthenia Gravis Foundation of America (MGFA) classification to decide the clinical type and the Quantitative Myasthenia Gravis (QMG) score to assess the severity of the disease.

Qualified physicians conducted the measurements at both baselines and after six months. The patients’ state was assessed using the following instruments:

The Hamilton Depression Rating Scale 17 Items (HAM-D) is a widely accepted tool used to evaluate the severity of depressive symptoms in clinical and research settings. The scale comprises 17 items designed to capture various facets of depression, including mood, guilt, suicidal ideation and somatic symptoms. Each item is scored based on the presence and severity of symptoms, with higher scores indicating greater symptom severity. With a total possible score of 53, the scores above 24 indicate severe depression. The scale’s established reliability and validity make it an essential tool for assessing depression, aiding clinical decision-making and research efforts to comprehend the underlying mechanisms and treatment outcomes linked to depressive disorders^(34,35).

The Hamilton Anxiety Rating Scale (HAM-A) is a commonly used instrument in clinical and research areas to evaluate the severity of anxiety symptoms. The scale consists of 14 items that assess different dimensions of anxiety, such as psychological and somatic symptoms. The rating for each item ranges from 0 to 4, with higher scores indicating greater severity of symptoms. The Hamilton Anxiety Rating Scale offers a systematic structure for healthcare professionals to assess the existence and severity of anxiety symptoms. This assessment tool assists in the process of diagnosing anxiety disorders, developing treatment strategies and evaluating the effectiveness of therapeutic interventions. The total score is calculated, resulting in scores ranging from 0 to 56. The scale for anxiety levels is as follows: 17 for mild anxiety, 18 to 24 for mild to moderate anxiety, and 25 to 30 for moderate to severe anxiety^(36,37).

The Quantitative Myasthenia Gravis (QMG) score was created to help doctors evaluate the specific deficits in MG patients, including tolerance and fatigue. The scale consists of 13 objective items, each rated on a scale of 0 (normal) to 3 (most severe), resulting in a total score between 0 and 39. The QMG assesses ocular (two items), facial (one item), bulbar (two items), gross motor (six items), axial (one item), and respiratory (one item) functions. Research suggests that a QMG score of 2 is a suitable cutoff for mild (QMG 0-9) to moderate (QMG 10-16) cases, while a score of 3 is appropriate for severe MG (QMG>16). In 2000, the Myasthenia Gravis Foundation of America (MGFA) made a significant recommendation, advocating for adopting the Quantitative Myasthenia Gravis Scale (QMGS) in all prospective studies assessing therapy for myasthenia gravis^(38-40).

2.3. Statistical analysis

The R program was used for the statistical analysis, version 4.2.3, Copyright (C) 2023 The R Foundation for Statistical Computing, R Core Team (2023). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria (https://www.r-project.org/).

First, we examined the potential correlations between the progression of myasthenia gravis, depression and anxiety in this group of patients.

The secondary objective was to investigate the response to therapy of patients with myasthenia gravis and depression, comparing the values of the QMG, HAM-D and HAM-A scales at the time of entering the study and six months after.

The endpoints were the values of the QMG, HAM-D and HAM-A scales, measured when the patients entered the study and six months after this moment.

To achieve the first objective, considering that possible associations are investigated between variables whose values are measured in the same patient at two-time points, to investigate the possible associations between QMG and HAM-D and HAM-A, we used a linear mixed model with a random intercept term, using R packages^(41-43), the dependent variable being the QMG value measured initially and at six months, while the independent variables were the HAM-D and HAM-A values measured initially and at six months, as well as other demographic and clinical variables measured at the beginning of the study. To achieve the secondary objective, paired t-tests were used to compare the values of the QMG, HAM-D and HAM-A scales at the initial time versus six months after this time.

The significance level a of the study was 0.05; p values lower than 0.05 were considered statistically significant.

3. Results

3.1. Demographic and clinical data

We enrolled 49 patients diagnosed with myasthenia gravis and a depressive disorder, with a mean age of 42.27 years old (SD=14.88); 37 (76 %) participants were female, and 12 (24%) were male. Almost half of them had a rural provenance (24; 49%), and 29 patients (59%) had a lower education. Regarding the age of the disease, the mean duration was 59.55 months (SD=66.98), 40 (90%) of patients had positive AChR antibodies, and 27 (55%) had undergone thymectomy. The descriptive statistical analysis of the study variables, including clinical and demographic characteristics, is detailed in Table 1.
 

Out of the 49 patients, 26 (53%) were already taking antidepressant medication before they were included in this study. Additionally, 20 patients required the introduction of antidepressant treatment, according to the multidisciplinary evaluation carried out during their current hospitalization, before being included in the study.

At baseline assessment, of the 49 patients, 25 (51%) were receiving treatment with escitalopram, seven (14%) with sertraline, six (12%) with tianeptine, and 11 patients (23%) with duloxetine. Moreover, 65% of these patients had associated anxiolytic treatment with buspirone, with doses ranging from 15 to 30 mg, and a mean dose of 19.8 mg. A total of 26 patients were treated for insomnia, with 16 of them receiving a combination of insomnia treatment and antidepressant medication. More precisely, mirtazapine and trazodone were employed to manage insomnia. Out of the total number of patients, 16 individuals (61%) received mirtazapine, while the remaining 10 patients were administered trazodone.

3.2. Temporal correlations between QMG, HAM-D and HAM-A

Table 2 compares the QMG, HAM-D and HAM-A scores at baseline and after six months, highlighting the changes in myasthenia severity and mental health status over time.
 

We notice that the averages of the variables are lower at six months, the difference being statistically significant.

The data indicate a statistically significant improvement in all three measured variables (QMG, HAM-D and HAM-A) over the six-month period. The reductions in scores for the QMG scale, HAM-D and HAM-A suggest that the treatment during this period improved the physical and psychological symptoms of the patients with myasthenia gravis.

3.3. Impact of depression, anxiety and clinical-demographic factors on myasthenia: simple and multiple linear mixed model analyses

In Table 3, we explore the intricate dynamics between the progression of myasthenia gravis and the evolution of depression, anxiety, and diverse clinical-demographic factors. Utilizing a simple linear mixed model, this analysis offers insights into how these variables intersect and influence the trajectory of MG, excluding random effects. Meanwhile, Table 4 expands upon these findings by identifying the predictors that emerged as statistically significant in the prior analysis. This subsequent examination incorporates them into multiple linear mixed models, now accounting for random effects, specifically emphasizing four pivotal predictors, and Table 5 presents a comprehensive overview of the predictive power of various factors within the studied model. Each predictor included in the analysis demonstrates a significant effect, as indicated by associated p values below the threshold of 0.10.
 

The model reveals the following:

• There is a positive association between QMG and HAM-D, with a decrease with 1 in HAM-D being associated with a reduction in QMG score by 0.58 points.
• There is a positive association between QMG and HAM-A, with a decrease with 1 in HAM-A being associated with a reduction of QMG score by 0.40 points.
• In patients with anti-AchR antibodies, the decrease in QMG is 5.9 higher.
• Influences of depression and anxiety scores HAM-D and HAM-A:
• There is a positive association between QMG and HAM-D, with a decrease with 1 in HAM-D being associated with a reduction of QMG score by 0.50 points, a statistically significant effect.
• There is a positive association between QMG and HAM-A, a decrease with 1 in HAM-A being associated with a reduction of the QMG score by 0.21 points, but the effect is marginally insignificant.

4. Discussion

The results of our study revealed a direct association between the severity of myasthenia gravis and the degree of depression and anxiety. At baseline, patients had a mean QMG score of 18.40, indicating a severe myasthenic deficit. This corresponded to a mean HAM-D score of 21.53 (SD=7.49), indicating a moderate degree of depression, and a mean HAM-A score of 13.31 (SD=9.51). These findings align with other research that highlights the complex correlation between the severity of myasthenia gravis and the associated psychological symptoms^(44,45).

The systematic review conducted by Gelinas et al. (2022)⁽⁴⁶⁾, based on an analysis of 67 published studies focusing on the human burden of MG on adults and their caregivers, confirms that individuals with more severe symptoms of myasthenia gravis are more likely to experience increased levels of depression and anxiety. Additionally, the longitudinal cohort study by Bogdan et al. (2020)⁽⁴⁵⁾ establishes a direct correlation between depression and disease severity, highlighting the nuanced interplay between mental health and myasthenia gravis progression. Notably, while initial disease severity does not predict relapses, ongoing psychological factors, such as anxiety and depression, along with disease severity, significantly impact fatigue⁽⁴⁷⁾ and overall quality of life in MG patients^(48,49). This underscores the importance of comprehensive treatment approaches that address not only the physical but also the mental health challenges faced by MG patients. By recognizing and treating the psychological symptoms associated with severe myasthenia gravis, healthcare providers can improve overall patient outcomes.

It is essential to be aware that emotional stress can significantly trigger the onset and relapse of various autoimmune diseases^(50-52), including myasthenia gravis^(53,54), when considering the link between mental state and MG. However, the relationship between stress and myasthenia gravis is not unidirectional; instead, it forms a complex and often vicious circle, so it becomes difficult to discern whether high depression scores actively trigger the course of myasthenia gravis or whether they are a consequence of the disease burden itself. However, on the one hand, stress can precipitate the onset or exacerbation of MG symptoms⁽⁴⁸⁾, highlighting the role of psychological factors in the manifestation of the disease. On the other hand, managing myasthenia gravis itself can cause significant stress in patients, exacerbating an already challenging emotional state⁽⁵⁵⁾. By breaking this cycle with comprehensive care methods, physicians may be able to manage MG’s physical and emotional effects, leading to improved patients’ outcomes and quality of life. This ambiguity underscores the need for comprehensive longitudinal studies that track both mental health indicators and disease progression over time.

The initial evaluation of MG patients was conducted during their hospitalization, when many were experiencing relapses. Elevated QMG scores indicated the severity of these relapses, often requiring higher doses of corticosteroids and pyridostigmine. Although corticosteroids are essential for managing MG symptoms⁽¹⁾, they are known to cause various behavioral and mood changes, such as insomnia, irritability and different levels of depression^(56,57). A cross-sectional study by Yasushi et al. (2011)⁽⁵⁸⁾ on 287 myasthenia gravis cases identified the dose of oral corticosteroids as a significant factor associated with a depressive state in MG patients. Factors such as disease severity, dose and duration of prednisolone, long-term treatment, and physical changes due to steroid use contribute to social disadvantages and a depressed state^(59,60). In long-term corticosteroid treatment for myasthenia gravis, the potential adverse reactions significantly impact the patients’ mental health, adding a complex layer to the management of these chronic conditions^(46,61). Due to physical alterations, patients may experience a decline in self-esteem and body image. These findings underscore the need for careful management of corticosteroid therapy in patients with MG. Addressing both the physical and psychological aspects of myasthenia gravis, including managing depression alongside escalating medication dosages, is crucial for mitigating disease severity and improving patient outcomes.

The study’s findings reveal that the average scores for the QMG, HAM-D and HAM-A were significantly lower at the six-month follow-up compared to baseline, indicating a marked improvement in both neuromuscular and psychological symptoms. Specifically, a reduction with 1 point in the HAM-D score was associated with a 0.58-point decrease in the QMG score. Similarly, a 1-point reduction in the HAM-A score was associated with a 0.40-point decrease in the QMG score. The multiple linear mixed model analysis reinforced the positive association between QMG and HAM-D, showing a statistically significant effect: a 1-point decrease in HAM-D was linked to a 0.50-point reduction in the QMG score. Although the association between QMG and HAM-A was also positive, the effect was marginally insignificant, with a 1-point reduction in HAM-A associated with a 0.21-point decrease in the QMG score. Additionally, for patients with acetylcholine receptor (AchR) antibodies, the decrease in QMG scores is notably higher, by an average of 5.9 points. This emphasizes the potential influence of immunological factors on the clinical outcomes of myasthenia gravis, indicating that patients with positive AchR antibodies might experience more significant improvements in myasthenic symptoms in response to treatment.

These associations suggest that improving depressive and anxiety symptoms correlates with a reduction in the severity of myasthenic deficits. Addressing mental health concerns such as depression and anxiety can directly influence the physical manifestations of myasthenia gravis, leading to a notable decrease in symptom severity. This dual approach highlights the mental and physical health interconnectedness in MG patients. When depressive and anxiety symptoms are effectively managed, patients often experience a reduction of myasthenic deficits, which in turn can improve their functional abilities and daily independence.

Conversely, improving myasthenic deficits through effective medical treatment can significantly enhance a patient’s quality of life. As the severity of physical symptoms diminishes, patients are likely to gain greater autonomy and control over their lives. As myasthenic deficits improve, the requirement for cortisone diminishes, which in turn contributes to an enhancement in the patient’s mental state. This increased independence can foster a more positive outlook and reduce the psychological burden of living with myasthenia gravis. As physical symptoms become more manageable, patients may experience a decrease in stress and anxiety. This creates a positive feedback loop where improvements in physical health further bolster mental well-being.

This relationship is complex, as the physical limitations and uncertainties associated with myasthenia gravis can exacerbate the depressive symptoms, while depression itself can worsen the perception and management of MG symptoms.

This bidirectional relationship suggests that an integrated treatment strategy, which simultaneously addresses myasthenic symptoms and mental health concerns, is essential for optimizing patients’ outcomes. Such an approach not only improves the immediate physical challenges associated with myasthenia gravis, but also supports long-term mental well-being, ultimately leading to a higher quality of life.

5. Limitations

The present article has several limitations. First, the study’s sample size (49 patients) is relatively small, which may limit the generalizability of the findings to the broader MG population. Furthermore, the sample was included from a single clinical environment, which may not represent the diversity of MG patients. Another possible limitation was the six-month follow-up period, which might be too short to observe the long-term effects of treatment on both myasthenia gravis and depressive symptoms. Thus, longitudinal studies with extended follow-up periods would provide more insight into the chronic nature of these conditions and their interactions. Another possible limitation is that, while the study included anxiety as a variable, it primarily focused on depression. The marginally insignificant effect of anxiety on myasthenia gravis (HAM-A scores) suggests a need for a more detailed exploration of this relationship.

Our study’s strengths include its longitudinal design, with a six-month evaluation period that offers a longitudinal perspective, and the utilization of validated assessment tools such as the Hamilton Depression Rating Scale (HAM-D), Hamilton Anxiety Rating Scale (HAM-A), and Quantitative Myasthenia Gravis (QMG) score, which ensures the reliability and validity of the study’s findings, and the statistical analyses, by employing linear mixed models and paired t-tests.

6. Conclusions

An extensive approach is required for managing the complex autoimmune disorder myasthenia gravis. This strategy should not only focus on the primary objective of reducing physical symptoms, but also attend to the mental well-being of patients. The correlation between physical and psychological well-being in myasthenia gravis is substantial and reciprocal, with each aspect significantly influencing the other. Efficient management of symptoms demands an effective treatment strategy that incorporates both medical and psychosocial therapies.

Psychiatric intervention plays a vital role in addressing the mental health aspect of myasthenia gravis. Regular psychological assessments should be incorporated into routine care for MG patients to identify and address depressive symptoms early. The interventions may include pharmacotherapy, such as antidepressants, and psychotherapy, including cognitive behavioral therapy (CBT), which can help patients develop coping strategies to manage both their physical symptoms and psychological stressors.

Moreover, multidisciplinary care teams, that include neurologists, psychiatrists and psychologists, can provide a more comprehensive approach to treatment. Such collaboration ensures that both the physical and mental health needs of MG patients are met, leading to more comprehensive and effective care. 

Institutional Review Board Statement: The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board, approved by the ethics committee of the Fundeni Clinical Institute, Bucharest, Romania. IRB number: 57523.

Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.

Data Availability Statement: All data reported within the article are available in anonymized form from qualified investigators upon request.

Acknowledgments: This scientific material is part of a larger study of a PhD thesis currently under development by the main author, Oana-Antonia Mihalache, from the Faculty of Medicine, “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania, with Sorin Riga as the thesis coordinator. We would like to thank all individuals who participated in this study.

Corresponding author: Cristian Petrescu E-mail: cristian.petrescu@drd.umfcd.ro