In the past years, depression and anxiety are rarely diagnosed early in their course in SLE, partially due to the lack of reliable and accepted screening metrics in this patient population, but also due to clinicians’ focus on the somatic symptoms. In a study by Mok et al., both depression and anxiety independently impacted the quality of life in SLE patients [10] . Therefore, finding out the prevalence of depression and anxiety in SLE patients allows us to make a better clinical decision with them. In this study, we analyzed depression and anxiety in SLE patients, and find that the prevalence of probable depression/anxiety based on PHQ-9/GAD-7 cut-off in SLE patients is 54.5% and 61.5%, respectively. These high ratios highlighted the importance of early diagnosis of these mental disorders in SLE patients.

In this study, we demonstrated that family income, disease activity, and manifestation in musculoskeletal and neuropsychiatric systems are related to depression. And in the meantime, disease activity, and manifestation in musculoskeletal and neuropsychiatric systems are associated with anxiety in patients with SLE. In previous studies, various factors have been linked to depression or anxiety in lupus, including age, antibody, fatigue, sleep quality, specific organ involvement, some cytokines, disease activity, glucocorticosteroid use, unemployment, and so on [11,12,13,14,15,16,17]. These diverse findings indicate that depression and anxiety in lupus are likely mediated through a complex mixture of biological, social, economical, psychological, and environmental contributors.

Of the numerous disease-related factors, the association between SLE disease activity and depression or anxiety remains one of the most frequently studied, though the results between studies are inconsistent. We demonstrated that the ratio of depression and anxiety varies in patients with different levels of disease activity. In fact, the ratio of patients with depression or anxiety in the moderate-to-severe disease activity group is much higher than in the mild disease activity or inactivity group, indicating that lupus disease activity is a risk factor for the severity of depression and anxiety. In line with our study, Nery et al. reported that SLE disease activity measured by SLEDAI was associated with depression severity [18], and Tay et al.[19] and Mak et al. [20] both found that increased SLE activity can be a prediction of more severe anxiety even after adjusting for depressive symptoms. However, Parperis et al. reported that despite the higher SELENA-SLEDAI score in the major depression compared with the group without major depression, this observation was not statistically significant [14] . In contrast, Jarpa et al. conducted a study showing that common mental disorders including depression and anxiety were not associated with lupus disease activity evaluated by SLEDAI [21] . This discordance in studies surrounding the effect of disease activity on depression and anxiety may have been attributed to differences in study methodologies, the diversity in screening instruments employed by the different studies, as well as varying definitions used for depression and anxiety disorders [22] .

The most contributive discovery of our study is the use of the SLEDAI score to predict the likehood of depression and anxiety in patient with SLE. To the best of our knowledge, this is the first study to predict depression and anxiety in SLE patients by disease activity. The discovery of the relationship between depression, anxiety, and SLEDAI score definitely helped rheumatologists better and earlier recognize patients with high risk for mental disorders. In fact, we may estimate depression and anxiety with screening tools in patients with active SLE. And we recommend that screening of depression and anxiety could be a conventional process in SLE patients with SLEDAI scores greater than 8.5. If the GAD-7/PHQ-9 score indicates moderate-severe anxiety/depression, we probably should initiate treatment of anxiety/depression in addition to corticosteroids and immune-suppressive drugs.

Our study had several limitations. First of all, it lacked longitudinal observations of subjects included in this study. Secondly, potential selection bias in who participated in the survey. Thirdly, the correlation of depression/anxiety symptoms with major depression/anxiety was not conducted in this study. Despite the methodological limitations and mixed results presented by the aforementioned studies, our research provides a rationale for future investigations.