Introduction
Large-scale epidemics of infectious diseases have been associated with a substantial burden on the mental health of the population [
1]. Although recent studies have not found convincing evidence for substantial increases in mental health symptoms during the COVID-19 pandemic compared to the pre-pandemic period [
2], trajectory studies show that the mental health of vulnerable groups such as women, young people, people with pre-existing physical ill-health, or those experiencing socioeconomic difficulties deteriorated more than the general population during the COVID-19 pandemic [
3,
4].
International migrant workers (IMWs) can be viewed as another group vulnerable to the consequences of the COVID-19 pandemic. IMWs are migrants of working age, who at some point were part of the labour force of the country they migrated to [
5]. Globally, there are 169 million IMWs, of which two-thirds reside in high-income countries [
5]. In the Netherlands, there are about one million IMWs, with over half of them coming from the European Union, primarily from Poland (CBS, 2022). IMWs often have a vulnerable position in society, working in so-called 3-D jobs: dirty, dangerous, and demanding (or demeaning or degrading) jobs [
6]. Compared to non-migrant workers, IMWs are more likely to work in essential, low-skilled occupations, have temporary contracts, work longer hours for lower wages, are willing to take on greater risks and have jobs that are not suitable for remote working [
6,
7]. Most often, they work in the service sector (e.g. wholesale and retail, transportation and storage), followed by industry and agriculture [
5]. During the pandemic, additional challenges for IMWs were, amongst others, limited social protection, high risk of exposure to and transmission of COVID-19, and impending job loss, in turn, leading to economic hardship and loss of housing (often provided by the employer) [
8].
Prior to the COVID-19 pandemic, mental health problems were already one of the most commonly reported work-related health problems among IMWs [
9,
10]. IMWs have been found to develop more symptoms of anxiety and depression than non-migrant workers [
11]. These common mental health problems have been exacerbated by the ongoing COVID-19 pandemic [
12]. Despite this mental health burden, access to specialist health care is limited [
10,
13]. IMWs can face various barriers related to seeking mental health services (e.g. lack of awareness of services, stigma) and to accessing the existing services (e.g. language differences, lack of culturally appropriate services) [
14,
15]. In light of the COVID-19 pandemic, there is thus an even higher need for psychosocial interventions for IMWs targeting the most notable symptoms of psychological distress, such as anxiety, depression, and posttraumatic stress disorder (PTSD) [
16,
17].
Scalable strategies and interventions such as those developed by the World Health Organization (WHO) may bridge the mental health treatment gap in vulnerable populations such as IMWs. These interventions are scalable because they are simplified and short versions of evidence-based psychological interventions for common mental disorders and can be delivered as (guided) self-help interventions (e.g. a book or online format) and/or by trained and supervised non-specialist mental health care workers [
18,
19]. Since the onset of the COVID-19 pandemic, there has been growing shift to the remote delivery of mental health services due to physical distancing and lockdowns [
4]. Human-guided digital interventions seem to be equally effective to face-to-face psychotherapy for the treatment of common mental health symptoms such as anxiety and depression [
20]. Policy makers, mental health professionals and service users have expressed interest in continuing with this remote delivery in the absence of pandemic-related measures [
21].
For this study, two WHO scalable interventions have been combined to be delivered remotely as a stepped-care intervention. In stepped-care interventions, individuals first receive an evidence-based, low-intensity treatment, i.e. a treatment requiring less of the individual’s and the professional’s time and which is less expensive [
22]. As patients’ progress is monitored, those not (significantly) responding to treatment step up to a treatment of higher intensity [
22]. In this way, stepped-care interventions have the potential to reach more people at the cost of fewer resources. Often, (guided) self-help treatments are used as a first step in stepped-care interventions, showing comparable effectiveness to face-to-face interventions [
23].
In this RCT of IMWs in the Netherlands, participants in the intervention group are offered a two-step, stepped-care intervention. The first step is a digitalized guided self-help web application (web app) of Doing What Matters in times of stress (DWM), an illustrated self-help book that is part of Self-Help Plus (SH +) [
24]. SH + is a guided self-help intervention based on acceptance and commitment therapy (ACT) that is delivered in five 2-h sessions to groups of 20–30 people. So far, SH + has been evaluated among refugee populations, showing overall beneficial effects in improving self-identified problems and well-being [
25]. For this project, DWM has been adapted for delivery in a digital smartphone-based format [
26]. The second step is Problem Management Plus (PM +), a transdiagnostic psychological intervention based on cognitive behavioural therapy (CBT) that addresses common mental health problems (e.g. depression, anxiety, stress) and self-identified practical problems (e.g. unemployment). Over five weekly face-to-face remotely delivered videoconferencing sessions, PM + teaches strategies to manage psychosocial problems [
27]. In previous randomized controlled trials (RCTs), PM + has been found to be effective in reducing psychological distress in low-income settings [
28,
29] and Syrian refugees in the Netherlands [
30,
31]. In addition to DWM and PM + , all participants, i.e. participants in both the intervention and control group, receive psychological first aid (PFA). PFA consists of humane, supportive, and practical help for individuals who have experienced a traumatic event [
32]. This stepped-care programme has also been found to be effective among healthcare workers experiencing psychological distress in the initial pandemic hotspots [
33].
Recent advances have been made in examining both digital markers and biomarkers either as correlates or as secondary treatment outcomes. Traditional assessment of psychological well-being and distress in IMWs through (online) questionnaires can be burdensome and time-consuming, while recently developed non-invasive, low-burden digital phenotyping measures that integrate voice, speech, movement and facial expression data from smart devices (e.g. smartphones) may be a promising and scalable way for assessing psychological wellbeing (e.g. depression, PTSD) [
34‐
36]. Notably, altered speech and vocality, reduced facial expressivity and movement have been found in major depressive disorder and psychopharmacological treatment has demonstrated restored levels of digital markers (e.g. increased head movement) and a decrease in anger and fear facial expressions [
37,
38]. Similarly, neuroendocrine correlates such as cortisol can be used as a non-invasive biomarker of physiological responses to chronic stressors. Hair cortisol concentrations (HCC) reflect hormone release over longer time intervals, as they indicate hormone secretion over several months [
39]. Studies have found that HCC is related to PTSD, depression and anxiety disorders [
40,
41] or with perceived job insecurity and work stress [
42,
43]. In recent years, HCC has also been used as a secondary outcome of psychological interventions [
44,
45].
This paper presents the study protocol for a randomised controlled trial in the Netherlands to examine the (cost-)effectiveness of the remotely delivered stepped-care DWM/PM + programme adapted for distressed IMWs living in the Netherlands. The final stage will consist of a process evaluation to assess the feasibility and acceptability of the intervention.
Trial monitoring and adverse events reporting
The project has an Ethics and Data Advisory Board (EDAB), that will monitor and advise on data management, and ethical, legal, and societal issues that arise within the project.
(Serious) adverse events ((S)AEs) are defined as any undesirable experience occurring to a participant during the study, regardless of its connection to the study procedure or the DWM/PM + intervention. All SAEs will be recorded in Castor EDC and reported to the EDAB and the Medical Ethics Committee of the Amsterdam University Medical Center (UMC), location VU University Medical Center (VUmc). The research team will follow up with all SAEs until they are stabilized or have abated. If necessary, participants will be referred to a general practitioner.
Participants can withdraw from the study at any time. No withdrawal criteria have been stated. Based on reported (S)AEs, the principal investigator (PI) can decide to discontinue participation in the trial.
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