Our study shows a continuous increase in number of visits to the CPOA from 2016 to 2023, mainly related to an increase in visits for anxiety and mood disorders. These findings agree with those of the CoviPrev study, which identified an increase in anxiety and depressive episodes after the onset of the COVID-19 pandemic [24]. The first pandemic restrictions had led to a reduction in number of emergency psychiatric consultations but was followed by a rebound in consultations [25], particularly among younger patients. This observation is reflected in our study, finding a meaningful reduction in the average age of patients consulting the CPOA and a more marked reduction in age after COVID-19. These results are consistent with data in the literature finding that young people were more affected by the COVID-19 pandemic, with an increase in malaise among young people in France [26, 27] and an increase in suicidal behavior among young people, especially young women [28]. In our study, the difference between the mean and median age remains stable over time, but indicates a distribution of consultation ages towards younger patients, consistent with the age of onset of psychiatric disorders [29].

Notably, the observed increase in consultations for depression and anxiety as well as the reduced age of ED populations had already commenced before the onset of the COVID-19 pandemic and has continued to increase linearly since then. Moreover, in our study the increase in the number of consultations seems to be even greater before COVID-19 than after. This observation agrees with a previously formulated hypothesis that COVID-19 only made a pre-existing situation worse [28] and indicates that additional general factors (social, economic, climatic, etc.) contribute to the exacerbation of the population’s distress [30, 31].

Other hypotheses could explain this increase in psychiatric emergencies. A first hypothesis is linked to the reduction in on-call services at other health facilities in Paris and the inner suburbs. Patients turn to the CPOA because they cannot be seen elsewhere or they are referred to the CPOA by other EDs because of no psychiatrist on duty in the establishment. A second hypothesis concerns the shortage of providers (psychiatrists and nurses) in CMHCs, which means that appointments often take several months, and the difficulties in accessing general practitioners, which could lead to patients with less serious pathologies presenting to psychiatric emergencies because they are unable to find a consultation in the short or medium term. This phenomenon is exemplified by the observed increase in the number of patients consulting a psychiatrist for the first time during their visit to the CPOA. Third, the increase in consultations to the psychiatric ED may also reflect an increase in the prevalence of anxiety and mood disorders in the general population, as previously outlined in other studies [24]. Finally, as a result of the various mental health awareness campaigns and the introduction of national suicide prevention numbers (3114) and telephone helplines (PsyIDF), patients are more likely to seek psychiatric care than they were a few years ago [32]. Another, more neurobiological hypothesis concerns the direct effect of Covid-19 on cerebral inflammation and the occurrence of psychiatric symptoms [33].

Paradoxically, although the number of visits to the psychiatric ED increased over the years, the proportion of total visits represented by hospital admissions decreased meaningfully, whatever the psychiatric diagnosis. The decrease in hospital admissions could be explained in part by the lack of available inpatient beds, forcing service providers to find alternative outpatient solutions and reduce the number of indications for hospitalization. Indeed, a recent DREES report showed a decrease in the number of psychiatric hospital beds over the last 3 years (-1000 beds or -3.1% in the public sector in 2021–2022) [34]. In contrast, as mentioned previously, a number of patients may consult EDs because of the difficulty in finding a consultation appointment, which would lead to an increase in outpatient referrals. Another hypothesis, similar to the one formulated previously, is that patients requiring outpatient care have difficulty finding consultations in the city and consult EDs instead. This hypothesis is consistent with the increase in the number of patients consulting a psychiatrist for the first time in our study.

The increase in number of psychiatric ED consultations, combined with the decrease in psychiatric inpatient admissions, suggests that outpatient care arrangements must be strengthened. At the CPOA, the introduction of post-emergency consultations by a nurse in advanced practice has allowed for providing follow-up care for patients in crisis situations while they wait for follow-up care at a CMHC, thus avoiding systematic recourse to hospitalization in certain cases [29, 35]. Also hospital sectors that have the impression that EDs are over-hospitalizing patients must be reassured that they are not. In reality, the data from our study show that we are able to manage more patients without a proportional increase in hospital admissions.

This study has a number of limitations. Although the CPOA is the largest psychiatric ED in France, this was a single-center study, which limits the generalizability of the conclusions to other institutions or regions. In addition, biases associated with the coding of emergency admissions may affect the accuracy of the data (classification bias). Differences in coding practices between the different practitioners working at the CPOA during on-call duty may have introduced a classification bias in that EDs are not the appropriate place to make an accurate diagnosis and there is may be some variability between practitioners. In addition, the ICD-10 coding system, which is grouped into broad categories, does not allow differentiation between certain diagnostic subcategories that might have been of interest for further study. In our study, only 6.3% of patients were seen in the ED after a suicide attempt, which is lower than in a general ED [36]; in fact, the CPOA does not receive patients who attempted suicide and require medical attention, and patients are referred to a general ED. In the literature, findings regarding post-COVID suicidal behavior are inconsistent [37]. However, in France, several studies have suggested an increase in suicide attempts among specific population groups, particularly young women [28]. Moreover, a number of patients consulted multiple times during the study period; it was not possible to extract their data independently. However, it would be interesting to do so in a future study to assess the influence of these repeat patients on psychiatric emergency department flow.