On March 17, 2020, the French government mandated a quarantine on its territory, as many other countries did. This lockdown forbade all non-essential movements to limit the spread of the COVID-19 pandemic and lasted 8 weeks until May 11, 2020. If quarantine is one of the oldest tools to control contagious diseases, evidence from previous epidemics suggests that it also has a negative impact on the mental health of the population (1).

The negative psychological effects of the COVID-19 pandemic and related quarantine were rapidly confirmed (2), notably in University students, whose vulnerability to mental health problems is well-known (3). In France, the first measurement time (T1) of the repeated cross-sectional COSAMe study, conducted during the first lockdown period (from April 17 to May 4, 2020), revealed high prevalence rates of severe self-reported stress (24.7%), anxiety (27.5%), depression (16.1%), and suicidal thoughts (11.4%) among the 69,054 French University students who responded to the survey (4). Recently, a French study found that students reported more frequently perceived stress (33.1% vs 22.1%), anxiety (24.0% vs 14.7%), and depressive symptoms (32.5% vs 16.2%), as well as suicidal thoughts (11.7% vs 7.6%) than non-students during this period (5).

Evidence from previous epidemics suggests that the negative psychological effects of quarantine measures can last or even worsen after the quarantine lift (1). A recent review by Aknin et al. reports that, after an early peak, the psychological distress may have declined (6). While some studies showed a return to pre-pandemic levels after the first lockdown, other studies reported that the prevalence rates of mental health disorders, while being lower than those measured during the lockdown period, were still higher than estimates obtained outside any pandemic context (7, 8). The Lancet's COVID-19 Commission Mental Health Task Force recommends monitoring the mental health of populations over the next few years given the many warning signs that persist, beyond the first times of the pandemic (6). There are notably growing concerns about suicidal behavior (9, 10). If several sources demonstrate little change in suicide during the early months of the pandemic (6), the negative consequences of the pandemic on suicidal behavior could be delayed due to barriers to care access during the early stages of the pandemic (11), or due to the delayed economic consequences of the crisis, which are usually associated with an increase in suicidal behavior (12). France is particularly affected by suicide, with nearly 9,000 suicides per year. Suicide is also the second leading cause of death among young adults (15–24 years old), and the first warning signs have already been reported among this population: the consumption of anxiolytics, antidepressants, and hypnotics has increased during the first year of the COVID-19 pandemic, compared to the five previous years (13).

The present study used data from the COSAMe survey, including those collected during the second measurement interval (T2) 1 month after the first quarantine was lifted (from June 15 to July 15, 2020). At this time, the total number of confirmed cases of COVID-19 in France was nearly 173,000, and nearly 30,000 deaths were attributed to COVID-19. The aims of the study were: (i) measuring changes in prevalence rates of self-reported mental health symptoms (stress, anxiety, depression, and suicidal thoughts) using repeated cross-sectional data, and (ii) identifying factors associated with mental health outcomes 1 month after the lift of the lockdown, adjusting for baseline mental health status, using longitudinal data.

This study revealed lower prevalence rates of severe symptoms of stress (21.7%), anxiety (22.1%), and depression (13.9%) among University students 1 month after the COVID-19 related quarantine was lifted in France when compared to the quarantine period (24.8%, 27.5%, and 16.1% for severe self-reported stress, anxiety, and depression, respectively). Conversely, the prevalence rate of suicidal thoughts increased from 11.4% of the students during the quarantine, to 13.2% 1 month after the quarantine was ended. Overall, four factors, which had already been identified as risk factors for mental health disorders during the quarantine (4), were significantly associated with poor mental health outcomes (suicidal thoughts, severe symptoms of anxiety, depression, and stress) 1 month after the COVID-19 related quarantine was lifted: female gender, a low feeling of integration, low quality of social ties, and a history of psychiatric follow-up.

Regarding anxiety and depression, our results are consistent with the decrease in prevalence rates obtained by Lu et al. (19) in the only study that compared prevalence rates of mental health symptoms during and after a COVID-19 related lockdown period, although using different samples (19). In line with the particular vulnerability of the University student population to the psychological impact of the quarantine, we found higher prevalence rates of severe self-reported symptoms of anxiety and depression (22.1% and 13.9%, respectively) than Lu et al. (6.3 and 6.8%, respectively) who conducted their study in the Chinese general population. Importantly, although these prevalence rates were lower 1 month after than during the lockdown, they remained higher than before the COVID-19 pandemic. Indeed, a study involving 4,184 French undergraduate University students in 2017 reported prevalence rates of 12.6% and 7.6%, for depression and anxiety, respectively (20).

Regarding suicidal ideations, several studies found high rates of suicidal ideations during COVID-19 related quarantine (4, 21) but the present study is the first to assess and show increased suicidal ideation after a quarantine lift. This result is in line with observations made by the French Institute of Public Opinion (IFOP), which found that 17% of the participants with lifetime suicidal ideations reported having experienced them after the quarantine, compared to 11% during the quarantine (overall 20% of the sample reported lifetime suicidal ideation) in a survey of 2,000 participants, representative of the French population aged 18 and over, carried out in September 2021 (22). Importantly, we found more frequent suicidal ideations among students who reported other severe mental health symptoms after the lift of the quarantine, which is consistent with the high prevalence of suicidal ideations in people affected by psychiatric symptoms and disorders (23), including during pandemic crises (24). Loss of income, feeling of integration, and quality of social ties, which are well-documented predisposing factors for suicide (12, 23), were also significantly associated with an increased risk of reporting suicidal thoughts after quarantine. The female gender is also a well-known risk factor for depression, anxiety, stress, and suicidal ideation in the general population (25, 26). Among University students, while literature is inconclusive concerning depression, many studies have also shown that female students are vulnerable to these disorders (27). Beyond genetic and biological factors, the pandemic context may have reinforced inequalities, including those based on gender, as has been shown in previous epidemics (28). Furthermore, although the sample is smaller and subject to a lack of power, the proportions of mental health disorders among non-binary participants were particularly high and should be the subject of in-depth studies.

Considering that stressful life events, including natural disasters, precede many suicides and suicide attempts (23) and because suicidal ideation is an indicator of future suicide attempts, psychiatric disorders, and global impaired functioning (29–32), particular attention should be paid to the high prevalence rates of suicidal ideation in the student population during the COVID-19 pandemic. Moreover, recent estimations predict an increase in the number of suicides based on the expected number of job losses due to COVID-19 (12). Several recommendations have been formulated using examples from countries that have efficiently broken the link between unemployment and suicide rates and notably promote: (i) access to secondary prevention (treat disorders such as depression), (ii) active labor market programs, and (iii) gender equality in the workplace (33).

Some limitations should be considered in the interpretation of these results. First, although the number of respondents is large, it represents 4.2% of French University students at T1 and 1.3% at T2. Caution is therefore necessary before generalizing these results. Nevertheless, this problem is encountered in all large epidemiologic studies and does not systematically mean that a self-selection bias has altered the results (34, 35). Indeed, it has been shown that a low response rate in epidemiological surveys only marginally affects prevalence and association measures (34, 35). Besides, the prevalence rates were stratified by and adjusted for gender and degree, and multivariate analyses included gender and degree as a covariate. To control for potential confounding bias related to differences in sample characteristics from one measurement time to another, the multivariate models included all covariates, and a subgroup analysis on the longitudinal data was performed. Second, although validated, the questionnaires used for this study to identify mental health symptoms are screening but not diagnostic tools. However, a high score on these validated tests is highly correlated with the presence of a mental health disorder. Finally, the questionnaire did not include other risk factors that could be associated with suicidal ideation, such as substance use disorder or personal or family history of suicidal behavior (36).

As a whole, two main conclusions can be drawn from the present study. First, severe symptoms of stress, anxiety, and depression were less prevalent after than during the COVID-19 related quarantine among University students but remained more prevalent than before the pandemic. Second, suicidal ideations, which were already frequent during the quarantine, were even more prevalent after the lift of the quarantine. This stresses the need to consider the psychological impact of the pandemic on students as a critical public health issue, demanding an urgent and strong policy response. Future studies will necessarily have to assess the long-term consequences of this enduring crisis, with a special focus on suicidal behavior.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Comité de Protection des Personnes Ile de France VIII. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

MW, GV, and FD'H contributed to the conception and design of the study. MW, CV, NM, and EH organized the database. CV and MW performed the statistical analysis. MW and FD'H wrote the first draft of the manuscript. All authors contributed to manuscript revision, read, and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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