The coronavirus disease 2019 (COVID-19) pandemic, as a result of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, has led to a public health emergency, thousands of deaths, generalised economic depression, unemployment and worldwide quarantines. Italy was the first European country to be severely impacted by the disease, with the total number of cases currently being 238,499, with 34,634 deaths. 1 On 8 March 2020 , in response to the growing pandemic of COVID-19 in the country, the Italian government imposed a national restriction of movements of the population, with the exceptions of buying food and other necessary items (e.g. drugs, disinfectants), essential work and health emergencies. 2 The national lockdown ended in June 2020 and proved to be useful in reducing the spread of SARS-CoV-2 infection.
However, such restrictive measures will likely have serious mental health effects on the population. 3e6 In particular, there are certain subgroups of the population that are particularly at risk in this situation due to their precrisis vulnerability. Among them, there are those who live in poor socio-economic conditions, 7, 8 those who are homeless, 9 migrant workers, 10,11 asylum seekers and refugees 12, 13 and patients with existing mental health disorders. 14, 15 In addition, some individuals will fall into several of these subgroups, thus increasing their risk. 16 For example, asylum seekers whose request of international protection has been rejected are often homeless, without documents, without jobs, live in poverty and also have symptoms of post-traumatic stress disorder (PTSD) due to their migratory experience, as well as depressive and adjustment disorders related to their present poor living conditions. This is not an unusual problem in Italy, and it has actually worsened over the last year due to a law removing the 'humanitarian' forms of permission of stay in the country and consequently the right for those people to be hosted in reception centres and get a job. 17 Previous research has shown that migrants in poor sociocultural conditions have an increased risk of mental health problems, including the worsening of PTSD, 18 higher rates of psychoses 19 and difficultly in access and/or inadequate treatment in some mental health services of the Italian National Health Service. 20, 21 There is evidence that the COVID-19 crisis has had a negative impact on the mental health of vulnerable populations through different mechanisms. 22, 23 Unfortunately, no data are currently available in specific populations, such as those investigated in this study; however, the authors recently performed a phone-based data collection survey (personal data, article in preparation) showing that there are several pathways leading to mental distress. For example, participants reported intrinsic effects related to anxieties of being infected; consequences of the quarantine, both on living experience (e.g. sense of imprisonment reminding traumatic experiences, intolerance to inactivity, boredom, depression) and interpersonal relationships (e.g. forced and conflictual cohabitation in reception centres); fears for the health of relatives living in their home countries; increased social marginalisation (e.g. homeless remained without food, clothing, furniture, laundry and washing facilities or without acceptance in public dormitories); job loss and additional economic difficulties; reduction of the activities in the mental health outpatient services, with increased difficulty in accessing them; increased fears of being taken by the police in the cases of undocumented migrants (the reduction of people around the city made them more visible in the streets) and inability to obtain necessary medications.
The aim of this study is to evaluate the impact of the COVID-19erelated lockdown on two specific problems possibly faced by mental health patients with a history of immigration and/or socioeconomic difficulties: that is, difficulties in mental health service utilisation and follow-up adherence. In particular, the study was conducted in an Italian public health outpatient service that was specifically dedicated to migrants and individuals with socioeconomic difficulties. The authors believe that this study is necessary because problems at this level have been predicted on the basis of theoretical considerations but, to the authors' knowledge, no evidence measuring this effect is currently available. Moreover, centres dedicated to migrants are frequently based on volunteers, and their reports often remain in the grey literature, thus remain difficult to access by the scientific community.
This retrospective study was conducted by the Mental Health Unit of the Italian National Institute for Health, Migration and Poverty (INMP), based in Rome. To facilitate access of migrants and homeless people, the INMP uses a low-threshold setting with a transcultural approach model. Information routinely and systematically collected in medical records was used, and all patients signed an informed consent form to use their data for study and research purposes.
The study included all patients who received at least one psychiatric interview in February (286 patients) and March (269 patients) in the years 2017e2020. Patients who visited the service in February were considered as the baseline population. Their sociodemographic data and diagnoses were considered in the sample description. Psychiatric disorders were categorised into eleven groups, reflecting the frequency of International Classification of Diseases (ICD)-9 disorders diagnosed in the healthcare unit (the ICD-9 diagnostic system is currently for official statistical recording used in Italy).
The number of patients who visited in February was also compared with those who visited in March for each particular year group. For 2020, the number of patients who visited in February and March was divided into three time periods of about ten days for each month (1-10th, 11-20th and 21-end of the month) to highlight the fact that the change started after the lockdown was established. Furthermore, to assess follow-up compliance, we used, as proxy, the number of patients who visited the service in February and then attended at least one follow-up visit the following month.
The sociodemographic characteristics and psychiatric categories of the study population are reported, and trends in the number of patients attending interviews are shown graphically. Continuous variables were computed as means ± standard deviations (SDs), and categorical variables were calculated as frequencies. Trend differences were reported as absolute numbers or percentage change when appropriate. In addition, the 95% confidence interval (CI) of percentage change was calculated and significance reported. Table 1 summarises the characteristics of the 286 patients who visited the mental health outpatient service in February. Participants were mainly men (75.17%) and had a mean age (±SD) of 37.37 (±13.43) years. Patient age and gender did not differ significantly between the study years. Geopolitical areas of provenance and diagnostic groups changed each year depending on unpredictable pathways of access related to the population dynamics, although the main provenance of Africa (above all Western/Central Africa) remained, and a prevalence for PTSD and depressive, adjustment and psychotic conditions was maintained. The proportion of Italians in poor socio-economic conditions who visited the outpatient service fluctuated between 5% and 10%.
As shown in Fig. 1 , there was a trend of increasing numbers of patients who visited the service between 2017 and 2020, until February 2020. Subsequently, a drop of the number of patients who visited in March was registered (Fig. 1) and, more specifically, a reduction in the number of psychiatric interviews after the 10th of March 2020, which corresponds with the period in which the lockdown was established in Italy (Fig. 2) .
In addition, whereas in the period 2017e2019, at least 30% of the patients who visited in February attended a follow-up visit in March of the same year; only 17.53% of patients accessing the mental health outpatient service in February 2020 came back for the scheduled follow-up appointment in March 2020 (Fig. 3) , showing a significant decrease of 46.57% (95% CI: 19.80 to 71.03; P < 0.001).
As a result of the COVID-19 pandemic and consequent lockdown, migrants and, more generally, individuals in poor socioeconomic conditions can experience a greater negative impact than the general population.
The first key factor is the psychopathological reaction to the situation (i.e. the COVID-19 pandemic). Indeed, in these subgroups of the population, difficult living conditions, together with previous experience of severe traumas and mental distress, are expected to increase levels of anxiety and consequently negatively impact mental health. 10, 12, 24 To the authors' knowledge, this feared effect on the mental health of migrants, refugees and homeless people has not yet been quantified, so further research on this issue is needed.
The second key factor is the difficulty in access to treatment if mental conditions are deteriorating, as expected. Theoretically, lockdown measures should not hamper the ability of receiving medical care, 2 and the Italian National Mental Health Service has modified its organisation and procedures to enable treatment of emergent needs. 25 However, factors such as insufficient information, 10 total quarantine in reception centres that report COVID-19 cases among their asylum seekers and other barriers to the access to mental health services 26 can limit the possibility of receiving adequate psychiatric help. To the authors' knowledge, this study is the first evaluation of the effect of the COVID-19 lockdown measures on the accessibility and follow-up use of public mental health services for immigrants and individuals with poor socio-economic conditions. It should be noted that, in some outpatient services, after the start of lockdown measures, appointments for psychiatric interviews were not available or were restricted only to emergencies. However, even during this period, the psychiatric service in the present study continued regular interviews on a free-access model; accordingly, the effects registered here are not due to changes in the organisation of the outpatient service but due to possible external factors (e.g. information about available facilities, movement restrictions). This study shows a relevant reduction in the total number of patients who visited the mental health outpatient service after the lockdown, with the risk that new mental health needs are neglected in a period when they are expected to increase. Moreover, a significant reduction in the number of follow-up visits has also been demonstrated, which has potential negative effects on therapeutic compliance and increases the risk of relapse.
This study is limited by that fact that it is a retrospective singlecentre study, so the findings cannot be directly generalised to other services. However, it has been reported that mental health services such as the one in this study, specifically oriented to migrants and individuals in poor socio-economic conditions, usually perform better than general mental health services in terms of both accessibility and patient satisfaction. 20, 21 Consequently, it is highly probable that the situation described in this study can be an indication of a more general issue for the entire National Health Service.
Owing to the relevance of these problems of accessibility and continuity of treatment for the mental health of the most vulnerable individuals in the population, proactive strategies should be implemented to monitor emergent needs and provide territorial assistance, with online assistance where feasible. 27, 28 Author statements
This study has been performed in accordance with the Helsinki declaration. The research design and ethical considerations were reviewed and approved by the Italian National Institute for Health, Migration and Poverty Review Board.