To the best of our knowledge, this is the first study to use network analysis to investigate the relationships between PHQ, GAD, ISI and PSS in the COVID-19 patient population. Based on this approach, this study developed a complex network consisting of four communities: the symptoms of depressive, anxiety, insomnia and perceived stress.
The participants of this study were confirmed COVID-19 patients from Shanghai Square Cabin Hospitals and their mental health status was investigated. Our analysis showed that the stronger edges were distributed within their respective symptom communities. It was consistent with previous studies [18, 36, 41, 42]. We found the strongest edge in the present network between ISI1 “Severity of sleep onset” and ISI2 “Sleep maintenance”. The results are controversial. Some scholars studied mental health in Chinese college students and residents of Macau under the COVID-19 pandemic, which supports our results [18, 43]. Other studies showed that the strongest edge appeared between ISI2 “Sleep maintenance” and ISI3 “Early morning wakening problems” in Hollander [44]. The inconsistent results may be due to the differences in research background, focus, and culture [18]. In the present network, the three strongest edges were all found between the ISI items, which indicated that sleep was the most prominent psychological problem among patients. After investigation, we found that patients' sleep problems are related to a variety of reasons. First of all, both the bad emotional experience and the unhealthy mental state could cause sleep problems. Secondly, the physical unhealthy symptoms also affected the patients' sleep. For example, poor sleep quality in COVID-19 patients is associated with slower recovery from lymphocytopenia and a longer hospital stay [45]. Finally, the environment of Square Cabin Hospitals was unconducive to sleep, such as prolonged lighting, noise, and irregular rounds. Five of the top ten edges were distributed in PSS items, which indicated that the patient was still under great pressure during the treatment process. And the node with highest predictability value was PSS7 “Control emotions”, this means that 88.6% of the explanation of PSS7 can be explained from within the network. The node with lowest predictability value was PHQ9 “Suicide”, this means that 46.2% of the explanation of PHQ9 can be explained from within the network.
Expected influences of nodes performed the importance of this node in the network. In the present network, ISI6 “Distress caused by the sleep difficulties”, ISI1 “Severity of sleep onset” and GAD3 “Excessive worry” were the top three nodes with the highest expected influences. So they are the three most important nodes in the present network, and we can alleviate other symptoms in the present network by improving sleep quality and reducing excessive worry [18, 41]. While patients were under medical treatment, they were separated from their families. Middle-aged patients often concerned about the elderly and young children. Other patients worried about the outcome of their treatment. The COVID-19 pandemic has indeed made a negative impact on the psychological state of people all over the world [46], and almost all mentioned changes in depression and anxiety state [47, 48]. Therefore, alleviating the patient's anxiety level also helps to alleviate other symptoms in the network. We also found central symptoms of psychological problems in the present network. The central symptom of stress problems was PSS10 “Overburden”. Reducing the amount of affairs piling up can relieve the perception of stress. Researches have shown that the perception of stress is directly related to the individual's sleep quality, anxiety, depression and other symptoms [49–51]. The central symptom of depressive problems is PHQ4 “Fatigue”, which means that providing some energetic activity or alleviating fatigue may help patients reducing depressive symptoms.
Bridge expected influences of nodes performed transmissibility between each nodes. The bridge nodes can be determined based on the value of the bridge expected influences of each node. So we identified seven bridge nodes, which were classified as depression, anxiety, and insomnia. PHQ2 “Sad Mood” was the top bridge node. This may due to more distress in patients, and activation of depression is more likely to cause other symptoms to co-occur. ISI1 “Severity of sleep onset” was the second bridge node, which indicated that difficulty falling asleep could indeed affect other symptoms in the present network. Logistic regression studies have shown that sleep problems are highly associated with poor mental health, particularly high anxiety [52]. PHQ3 “Sleep” was the third bridge symptom, which was highly correlated with insomnia symptoms. Expected influences and bridge expected influences provides a target for reducing the complex symptoms of stress, depression, anxiety and insomnia in COVID-19 patients. Based on the core symptoms and bridge symptoms, we believe that improving sleep and reducing worry and depression can effectively regulate other symptoms in the network.
We found that women were more susceptible to insomnia than men, which was consistent with the results of previous studies [52, 53]. Women had significantly higher levels of perceived stress, depression, anxiety and insomnia than men. Therefore, women and men had different network structures. In the male network, ISI6 “Distress caused by the sleep difficulties”, GAD6 “Irritability” and ISI2 “Sleep maintenance” were the most central symptoms influence. It may be that men suffer more from insomnia and are prone to mood of anger, which may suggest that improving men's sleep quality and controlling their emotions can reduce other symptoms in the network. In the female network, GAD5 “Restlessness”, GAD1 “Nervousness” and ISI6 “Distress caused by the sleep difficulties” were the most central symptoms influence. Women are emotionally sensitive and easily interference with all sorts of events. Reducing the amount of interference women experienced can alleviate other symptoms in the network. A common symptom in both sexes was distress caused by insomnia, with men more likely to be angry and women more likely to be jittery.
We replicated the work of Bai et al., and found that the same network (insomnia- anxiety-depressive network) was structured differently in different populations [18]. In their study, the core symptoms of the network were ISI2 “Sleep maintenance”, GAD4 “Trouble relaxing”, ISI7 “Interference with daytime functioning”. And what we found was that ISI6 “Distress caused by the sleep difficulties”, GAD4 “Trouble relaxing”, GAD5 “Restlessness” were the core symptoms of the network. Although Macao residents in Bai's study were under the shadow of COVID-19, their lives and work were not completely restricted. They had anxious, trouble relaxing, insomnia and had their lives and work affected because of the fear of being infected with COVID-19. COVID-19 patients in Shanghai Square Cabin Hospitals had their movement restricted in the hospital and were medical treated in a completely different environment from their lives before. They worried about the outcome of their treatment, their separated relatives, and insomnia, etc.. So they became restlessness, trouble relaxing and had the pain caused by insomnia. By comparing the bridge symptoms of the two networks, the bridge symptoms of previous studies were PHQ3 “Sleep”, GAD5 “Restlessness”, GAD6 “Irritability”, ISI1 “Severity of sleep onset”, PHQ8 “Motor” [18]. Our research shows that ISI1“Severity of sleep onset”, ISI7 “Interference with daytime functioning”, GAD1 “Nervousness”, GAD7 “Felling afraid” and PHQ8 “Motor” were the bridge symptoms. The bridge symptoms of COVID-19 patients and Macao residents are not exactly the same. The bridging symptoms of the former are mainly anxiety and insomnia, while the latter are mainly depression and insomnia, which means that the particular symptoms most critical to reduce the risk of contagion between psychiatric syndromes within the network models are not exactly the same.