How much of an impact did COVID-19 self-isolation measures have on mental health?

It has been argued from various angles that many people have been psychiatrically damaged by the COVID-19 pandemic (Tandon, 2020).

Because neither an effective treatment nor a vaccine exists, in order to save lives, treatment has centered on relieving symptoms. As to prevention, countries in the midst of the epidemic have taken measures to shut down travel by locking down cities and confining individuals to their homes. Meanwhile, even countries that have the spread of the virus somewhat under control are attempting to get people to keep their contact with others to a minimum through “social distancing.” These measures have increased social isolation and brought economies to a standstill, thereby causing economic hardship for many due to unemployment or lost income. As a result, many different authorities, including the World Health Organization (WHO, 2020), have called attention to the need to provide care for people’s mental health.

Unfortunately, there is no clear answer to the question of how much impact the pandemic has had on people’s mental health. Undeniably, although gradual, a few pieces of evidence regarding its impact have come to light (Keep Mental, 2020); for instance, it has been reported that nearly half of China’s healthcare workers in charge of caring for COVID-19 patients complained of depressive symptoms (Lai et al., 2020). In addition, Rogers et al. (2020) have investigated the psychological impact of COVID-19 on affected patients with a meta-analysis. Nevertheless, our search for studies using objective indicators to assess the impact on society found none. On the other hand, in this magazine, there are many discussions about "opportunities and challenges of telepsychiatry and mental health apps" (Tandon, 2020; Ramalho et al., 2020).

Thus, we conducted a study using a smartphone application that we developed and was available to the public to assess a person’s voice stress during their telephone calls (Tokuno, 2018). The application analyzes all the user's voice during call, anonymizes the results and stores them in the cloud system. Therefore, we and the user have no control over the analysis. Based on data collected by this application, we investigated how isolation affected stress levels in a sample of Japanese people.

Data were collected from December 29, 2019 to June 6, 2020. The sample consisted of 126 Japanese users of the application (out of 5,246 application users) who continuously used its automatic call analysis function on an Android operating system smartphone. That is, 126 users had installed the application by December 29, 2019 and made at least one call a week until June 6, 2020 without uninstalling it. For this study, we only used an indicator calculated from call analyses for at least three calls. Finally, this study used an analysis of 8,669 calls by 90 users. We used anonymized data that complies with the application's user agreement and company privacy policy, so subjects agreed to use their data but do not know if their data was used Fig. 1 .

Fig. 1

Change in voice stress mental health indicator due to COVID-19 pandemic.

The graph shows the weekly means and their standard errors. The gray background represents the period of outing restrictions. (i) First case of infection reported in Japan. (ii) Charter plane brings 206 Japanese back from Wuhan. (iii) The WHO declares a public health emergency; the quarantine of the Diamond Princess cruise ship begins. (iv) Elementary, middle, and high schools closed. (v) The governor of Tokyo mentions lockdown. (vi) State of emergency declared (voluntary isolation at home). (vii) State of emergency extended. (viii) State of emergency lifted.

There was no clear correlation between the number of patients reported and mental activity.

In the graph shown, lower mental activity indicates a lower energy level, that is, that the subjects were feeling stressed in some way. As one can see, with each pandemic-related events, there were decreases in the activity level, however, the fluctuations were not large, and the declines were temporary. Some events are increasing mental activity. Evacuation from Wuhan (ii) seems to have been taken as a pleasure. In addition, the Governor of Tokyo's press conference (v) was announced immediately after the holidays, so it seems that the influence of the holidays was strong at that time. From there, anxiety began to reduce mental activity. The most striking decline was when people began to self-isolate at home. After that, mental activity began to recover at the time when the state of emergency was extended (vii), and when the state of emergency was lifted (viii).

This study showed whether there was a psychological impact on the general Japanese population and not a specific group, such as infected people or health care workers. It is also unknown whether the sample included infected people or medical workers because the analysis was based on anonymous information. Of course, changes in the average level of mental activity for this group do not indicate which individuals may have needed mental-health care. Further screening is therefore needed to identify people unable to recover from pandemic-related stress.

Furthermore, in Japan, cities were not forcibly locked down nor were people forcibly confined to their homes. Rather, based on the public’s autonomy, people were asked to voluntarily refrain from going out as much as possible for a month and a half. Even if one considers this a reasonable response in a pandemic, the impact of more stringent restrictions in Europe and the United States may have been more considerable.

Financial disclosure

S Tokuno received financial support from PST Inc. until September 2019, and has not received additional financial support thereafter. Y Omiya declares no conflict of interest. All authors contributed equally to this letter.

Declaration of Competing Interest

The authors report no declarations of interest.