**4. Discussion**

When searching medical databases, we did not find any other study that compared mental health factors during the SARS-CoV-2 pandemic between people with and without SLE.

The current outbreak of SARS-CoV-2 infection has led to global changes in many dimensions of our daily lives. Ubiquitous information about the number of deaths, new diseases, diseases predisposing one to a severe and unfavorable course of SARS-CoV-2 infection, lack of targeted treatment, social isolation, change of existing habits, long-term quarantine, and a limited or total lack of access to goods or medical support does not only raise public health concerns but also causes a huge mental burden by generating emotional stress and elevated anxiety. It is widely assumed that the pandemic has aggravated depression, anxiety, and related sleep disorders.

In this study, a significant number of participants experienced symptoms of anxiety, depression, and insomnia, with a 100% prevalence of these symptoms in the group of people with SLE—this is different from the frequency of these disorders in other studies [8,12,27,28]. This may be due to the fact that our study was conducted in Europe where an infection problem on such a scale has not occurred for nearly 100 years, while the aforementioned studies were conducted in Asia where epidemics have been more frequent. This has meant that the institutions responsible for organizing the protection of public safety in China, Hong-Kong, and Taiwan have well-prepared procedures, well-trained service personnel, as well as an entire industry that is capable of adapting to the goal of fighting a pandemic. These differences may also arise from the different tools used to assess depression, anxiety, or sleep disorders and from the differences in the project design itself.

Epidemiological data provide evidence of a steady increase in autoimmune diseases over the last decade. It has long been known that autoimmune diseases show clear gender differences [29], with many more women contracting these diseases than men [30]. The effect of age varies, depending on the disease. According to the study by Fairwather et al., the majority of autoimmune diseases manifest themselves before the age of 50 and are characterized by acute cellular pathology, whereas those manifesting after 50 are characterized by chronic inflammation and fibrosis [31]. These findings concerning age and gender are consistent with the findings of this study, in which people with a diagnosed SLE were significantly younger and more frequently female compared to people without the SLE.

In recent years, many studies have been conducted on the relationship between anxiety, depression, and sleep disorders in patients with chronic diseases. It has been observed that patients with chronic diseases often exhibit mental disorders [32]. In the study conducted by Polukandrioti et al., it was noted that at least 20% of patients with coronary artery disease showed symptoms of anxiety and depression [33]. Other studies confirmed the same relationship in patients with chronic neurological diseases, chronic pain, kidney diseases, and respiratory diseases [34–39].

The most important discovery of our study is the fact that despite the significantly more frequent occurrences of chronic diseases in the group of people without a diagnosis of SLE, it was the group of patients with SLE that showed elevated symptoms of anxiety, depression, and sleep disorders (*p* < 0.001, *p* < 0.001, *p* < 0.001, respectively). These individuals, when the results were adjusted for age, gender, chronic diseases, and smoking, showed more than a 3.6 fold increase in the risk of anxiety symptoms, a more than 4.1 fold increase in the severity of depression symptoms, and more than a 6.7 fold increase in the severity of sleep disorders. An autoimmune disease in itself is a source of many stress factors, including reduced activity and fulfillment of social roles at home and work, financial difficulties related to reduced income and high costs of medical care, changes in external appearance resulting, among others, from complications of the applied immunosuppressive treatment, loss of independence, and impaired interpersonal relations [40]. Even slight intensification of the influence of everyday stress factors in people with autoimmune diseases may intensify the symptoms of the disease, i.e., adversely affecting the time of remission [41].

This is why patients with a diagnosis of SLE, even after adjusting for those differences in co-occurring conditions have more severity anxiety, depression, and sleep disorders, as confirmed by our study.

Our study had several limitations. First of all, it lacked longitudinal observations in people included in this study. Secondly, the number of respondents was limited. Thirdly, it was impossible to determine a correlation between the presence of anxiety, depression, insomnia, and a specific type of other autoimmune disease. Fourthly potential selection bias in who participated in the survey. This means that a longitudinal, multi-center study with a greater number of respondents is required.
