Abstract
This is the protocol for a Campbell evidence and gap map. The objective of the map is to map available systematic reviews on the effectiveness of treatments for depressive disorders among adults. Specifically, this EGM includes studies on the effectiveness of treatments across a range of outcome domains.
BACKGROUND
Introduction
The problem, condition, or issue
Depressive disorder is characterized as feeling sad or having a depressed mood, having feelings of worthlessness or guilt, experiencing loss of interest, pleasure, or energy, having increased fatigue and lack of physical activity, and having difficulty thinking, concentrating, or making decisions (American Psychiatric Association, 2013; World Health Organization, 1993).
Depression is a common mental disorder affecting 3.8% of the population (approximately 280 million people) and 5.0% of adults worldwide (Institute of Health Metrics and Evaluation, 2021). It accounted for over 50 million Years Lived with Disability (YLD) in 2015. More than 80% of this mental burden occurred in low- and middle-income countries (World Health Organization, 2017). This disorder can be long-lasting or recurrent and can dramatically affect a person's ability to function and live a rewarding life. It is the single largest contributor to non-fatal health loss (7.5% of all YLD) and suicide globally (Jacob, 2014; World Health Organization, 2017).
According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), depressive disorders include disruptive mood dysregulation disorder, major depressive disorder (including major depressive episodes), persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, substance- and medication-induced depressive disorder, depressive disorder due to another medical condition, other specified depressive disorder, and unspecified depressive disorder (American Psychiatric Association, 2013). As disruptive mood dysregulation disorder is more frequent among children and adolescents than adults, it is not considered in the present study, whereas the other depressive symptoms will be included. Although bipolar depressive disorder was separated from depressive disorders in DSM-V, it will also be included in the present review due to its high frequency among adults (American Psychiatric Association, 2013).
The intervention
Depressive disorders have attracted worldwide attention (Belkin, 2016; Saxena, 2019), and many programs have been developed to prevent this mental health crisis, such as Manochaitanya (Manjunatha, 2016), President's Program (Mirza, 2019), and the mental health Gap Action Program developed by the World Health Organization. The recommendations for the general adult population provided by the APA Guideline Development Panel identified three types of treatment for initial or relapse depression: psychotherapy, pharmacotherapy, and complementary and alternative treatments (American Psychological Association, 2019). In more detail: Psychotherapy is any psychological service provided by a trained professional that primarily uses forms of communication and interaction to assess, diagnose, and treat dysfunctional emotional reactions, ways of thinking, and behavior patterns. Psychotherapy may be provided to individuals, couples, families, or members of a group (American Psychological Association, 2015). There are many types of psychotherapy. The main approaches generally include behavioral therapy, cognitive therapy (including cognitive, cognitive-behavioral, and mindfulness-based therapy), interpersonal psychotherapy, psychodynamic therapy, and supportive therapy (American Psychological Association, 2019). Pharmacotherapy refers to the use of pharmacological agents in the treatment of mental disorders (American Psychological Association, 2015), and second-generation antidepressants such as venlafaxine, trazodone, bupropion, and mirtazapine are recommended in the guideline (American Psychological Association, 2019). Complementary and alternative treatments, also called complementary and alternative medicine (CAM), are a group of therapies and healthcare systems that fall outside the realm of conventional western medical practice. These include but are not limited to acupuncture, chiropractic, meditation, aromatherapy, homeopathy, naturopathy, osteopathy, touch therapy, reflexology, reiki, and the use of certain dietary supplements (American Psychological Association, 2015).
There are many treatments for depression, but more than 75% of adults from low- and middle-income countries receive no treatment (Evans-Lacko, 2018). Furthermore, evidence regarding the effectiveness of interventions is not uniform, covering different intervention types, settings, and target populations and making it difficult to navigate (Gabriel, 2022; Lee, 2022; Wickersham, 2022). Therefore, this study aims to produce an evidence and gap map (EGM) of systematic reviews, based on the Campbell Guidelines of EGMs (White, 2020). Specifically, this study seeks to produce an EGM of systematic reviews concerned with interventions for the treatment of depressive disorders. This EGM is designed to collect and display all systematic reviews that reported the effectiveness of interventions to treat depressive disorder to inform research commissioning and provide a scientific basis for the development of healthcare policies and practices.
Why it is important to develop the EGM
Although the American Psychiatric Association (APA) had released guidelines for the treatments of depression (American Psychological Association, 2019), not all interventions were considered, particularly in the era of rapid development of science and technology. For instance, several new therapies have emerged that may be a better choice for some patients, such as animal-assisted therapy (Majić, 2013), virtual reality exposure therapy (Baghaei, 2021), and e-mental health apps (Porras-Segovia, 2020). However, updating guidelines is time-consuming and costly. Moreover, the “best treatment” is not only determined by effectiveness but also by resource availability, patient preferences, and doctors' experience. Hence, whilst waiting for updated guidelines an EGM is a useful starting point for decision-makers and members of the public seeking evidence-based advice.
The EGM is a table that offers a visual presentation of the available evidence for a particular sector. The map provides an overview of what studies are available but does not summarize the findings. It is a decision-making and research priority-setting tool that highlights gaps in research and provides information for strategic health and social policies, programs, and research priorities (Saran, 2020; White, 2020). It is estimated that 85% of research investment is wasted, and some of these problems can be avoided by prioritizing research, including using systematic reviews (SRs) to rigorously evaluate available evidence before funding or conducting new research (Chalmers, 2014). EGMs can be used to avoid unnecessary duplication and determine whether there is sufficient evidence on which to base decisions or sufficient research for knowledge synthesis (Snilstveit, 2016).
Existing EGMs
We searched the Campbell Library, Cochrane Library, PubMed, EPPI, and 3ie (International Initiative for Impact Evaluation) and identified two EGMs related to the treatment of depression (Britton, 2021; Campisi, 2020). Campisi et al. (2020) created an EGM regarding micronutrients for depression among children and adolescents with 30 primary research publications. They found that the most frequently studied micronutrients were vitamin D, zinc, iron, folate, and vitamin B-12. Britton et al. (2021) collected evidence on mindfulness-based interventions for depression and interpreted its mechanisms with the self-related processes, including self-concept, rumination, self-compassion, self-efficacy, and self-esteem. Whether using participant or intervention studies, these two EGMs did not meet the need among adults with depressive symptoms. Therefore, it will be useful to develop an EGM on the treatments for depression among adults.
OBJECTIVES
The objective of the map is to map available systematic reviews on the effectiveness of treatments for depressive disorders among adults. Specifically, this EGM includes studies on the effectiveness of treatments across a range of outcome domains.
METHODS
EGM: Definition and purpose
This EGM is an effectiveness map of interventions for depression, in which the primary dimensions are intervention categories (rows) and indicator domains (columns). Secondary dimensions, such as country and target group, are included as filters (White, 2020). We will adapt EGM methods from various key studies (Bragge, 2011; Snilstveit, 2016; White, 2020) and utilize a five-stage process: Define a framework, which determines the scope and inclusion and exclusion criteria; Identify available evidence (search). Appraise the quality of evidence. Extract, code, and summarize the data that relate to the objectives. Visualize and present the findings in a user-friendly format.
We will use the EPPI-Mapper mapping tool developed by the EPPI-Centre to display identified studies using the framework described below.
Framework development and scope
After discussions and recommendations with stakeholders and advisory panels on August 8, 2022, a framework for the main classification items of different intervention populations and groups was finalized. We further defined the scope and framework for consultation with our research group, which included researchers from evaluation and evidence synthesis (HW and YKH), education (GLP), public health (LJY), psychiatrist (WW), and psychotherapist (QK and XZ). Finally, the EGM will include two dimensions of the framework: interventions and indicators/outcomes. We will follow the standard EGM framework as a matrix where the rows are intervention domains and the columns are indicator/outcome categories.
Stakeholder engagement
The group members for this EGM include researchers from evaluation and evidence synthesis (Howard White), education (Liping Guo), public health (Jieyun Li), health and wellbeing (Kehu Yang), health statistics and services (Yaogeng Chen), doctors of psychiatric (Wen Wang), and psychotherapist (Kun Qiao and Zheng Xu). Feedback from the group members was received and assimilated into the framework plan at the title registration stage. The stakeholders will be engaged at all stages of the EGM to review and comment on interventions, studies, outputs, map findings and provide advice on dissemination channels.
There has been extensive stakeholder engagement in the preparation of the framework. This has included: Stakeholders' online consultation meetings at least bimonthly in discussing the direction and scope of EGM. One-on-one calls with stakeholders not able to attend the larger stakeholder consultations. Three rounds of piloting and revising the coding framework using selected eligible or ineligible studies. The details were shown in Tables 1–3. Further stakeholder consultation is planned for January 2023.
Each of these intended users has participated in defining the intervention and outcome framework. The participation of the advisory group members will contribute to greater alignment of global and national efforts in forming the basis for improving the evidence base on depressive disorder.
Conceptual framework
Depression can result from a complex interaction of psychological, physical, behavioral, and other factors (Pandey, 2021; Ratanasiripong, 2012; World Health Organization, 2017), and there are various treatment mechanisms (Britton, 2021; Xie, 2021). For example, pharmacotherapy mainly reduces the activity of brain nerves by reducing neurotransmitters in the body, thus stabilizing the mood of patients with depression; psychological therapy as well as educational program and training aim to correct cognitive bias, improve behavioral coping ability, and promote positive behaviors to empower the suffers of depression. Besides, relieving physical pain, relaxing the body, and balancing nutrition are complementary treatments for depression. The conceptual framework for depression is shown in Figure 1. The present EGM aims to provide a classification of treatments for depression.

Conceptual framework for depression.
Dimensions
EGM framework interventions
This EGM focuses on systematic reviews of effectiveness studies of interventions, with a primary aim of treatment or reducing depressive disorder in adults. The intervention-outcome framework identified four categories of intervention groups based on the type of interventions. Each category has several subcategories based on the pilot coding of 30 studies, expert advice, and discussion among the team and advisory members.
Table 4 lists the intervention categories, subcategories, and definitions. There are four categories of intervention: psychotherapy, pharmacotherapy, complementary and alternative treatments, and other interventions. The psychotherapy category comprised seven sub-categories: behavioral therapy (BT), cognitive therapy (CT), cognitive behavioral therapy (CBT), interpersonal psychotherapy (IPT), psychodynamic psycho-dynamic psychotherapy (PP), supportive psychotherapy (SP), other psychotherapy; the pharmacotherapy covered eight sub-categories: selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), tetracyclic antidepressants (TeCAs), norepinephrine and dopamine reuptake inhibitors (NDRIs), serotonin antagonist and reuptake inhibitors (SARIs), and other antidepressants; the complementary and alternative treatments include five sub-categories: physical therapy (PT), physical activity (PA), art therapy (AT), traditional Chinese medicine (TCM), and dietary supplement; and the other intervention comprised educational program and training, e-mental health apps and other treatments.
Studies used during piloting: Characteristics of included studies.
Continue: Studies used during piloting: Characteristics of included studies.
Studies used during piloting: Characteristics of excluded studies.
Intervention categories and sub-categories.
EGM framework indicators/outcomes
For inclusion, the primary aim of the systematic review is to assess the effects of interventions on depressive symptoms in adults as a primary indicator/outcome. The indicator/outcome domains and sub-domains are the main categories and subcategories, used as column headings in our map.
The most common outcomes are remission of depressive symptoms (i.e., dysregulation disorder, major depressive disorder, persistent depressive disorder, premenstrual dysphoric disorder, a depressive disorder with another medical condition, and bipolar depression), symptoms of depressive disorder (anxiety, stress, suicide intention, and sleep disturbance), life and social skills (quality of life, physical function, and social function), and adverse events of pharmacotherapy and other treatments. See Table 5 for the list of outcomes, definitions, and examples.
Indicator/outcome domain.
EGM framework population dimension
The primary population of interest for this map is adults (over 18 years old). We will sub-categorize the adult population according to age group, gender and sexual orientation, career, and health state (as shown in Table 6). The population dimension will be listed as a filter. For studies assessing effects with people who are providing services, we will sub-categorize according to whether they are professionals or volunteers.
Population dimension.
Inclusion and exclusion criteria
Types of study design
We will include only systematic reviews that conduct meta-analyses of randomized controlled trials (RCTs). According to the definition of systematic review from Campbell Collaboration and our objective, a systematic review met the following four criteria will be included: (1) clear inclusion and exclusion criteria; (2) an explicit search strategy; (3) systematic coding and analysis of included studies; (4) meta-analysis. If a systematic review included the primary studies using RCT and quasi-experimental designs (QED), we will only include the data from RCTs.
Protocols for ongoing research will be included. Qualitative reviews, integrative reviews, rapid reviews, reviews of reviews, and evidence synthesis/summaries are beyond the inclusion criteria. Primary studies are excluded.
Types of intervention/problem
We will include systematic reviews assessing any interventions with an explicit aim of reducing depressive symptoms, including educational programs and training, psychotherapy, physical therapy, pharmacological treatment, physical activity, and any interventions that aim to treat depression in adults.
Types of the population
The target population is adults (aged 18 and over) with depressive symptoms including those with any other mental and/or physical problems, and professionals or volunteers providing services to the target population. If a review covered both adults and children, we will extract the independent information on adults if available.
Types of outcome measures
We will include systematic reviews that assess the effect of interventions on depressive symptoms and related symptoms, such as anxiety, stress, suicide intention, life and social skills, and adverse events by the pharmacy or other treatments.
Other eligibility criteria
Studies will not be limited by geographic location. Due to the limitation of team members, only studies published in English and Chinese will be included. There is no restriction on publication time.
Types of location/situation (as applicable)
Not applicable.
Types of settings
Any settings, such as hospitals, communities, and institutions, will be included.
Search methods and sources
The search for EGM will be conducted in three stages: Stage 1: Pilot for screening and coding of included studies (deadline: January 2023). Stage 2: Search for relevant systematic reviews from academic databases and international organizations (deadline: February 2023). Stage 3: Search for additional websites for gray literature after expert consultation (deadline: March 2023).
Database search for stage 2
The following international electric databases will be searched: Social Sciences Citation Index (via Web of Science) ScienceDirect (https://www.sciencedirect.com/) Taylor & Francis Online Database (https://www.tandfonline.com/) JSTOR (https://www.jstor.org/) PsychArticles (via ProQuest) PsychInfo (via EBSCOhost) OCLC FirstSearch (https://firstsearch.oclc.org/) PubMed (https://pubmed.ncbi.nlm.nih.gov/) EMBASE (https://www.embase.com/) The Cochrane Library (https://www.cochranelibrary.com/) The Campbell Library (https://www.campbellcollaboration.org/better-evidence.html) 3ie Systematic Review Database (https://www.3ieimpact.org/evidence-hub/publications/systematic-reviews) Epistemonikos (https://www.epistemonikos.org/) CNKI (https://www.cnki.net/)
In addition, the pre-print repository MedRxiv (https://www.medrxiv.org/) will also be searched
Below, the search strategy for PubMed is provided:
“Depressive Disorder”[Mesh] OR “Long-Term Synaptic Depression”[Mesh] OR “Depression, Postpartum”[Mesh] OR “Depressive Disorder, Treatment-Resistant” [Mesh] OR “Bipolar Disorder”[Mesh] OR “Dysthymic Disorder”[Mesh] OR “Seasonal Affective Disorder”[Mesh] OR “Depressive Disorder, Major”[Mesh] OR “Adjustment Disorders”[Mesh] OR “Affective Disorders, Psychotic”[Mesh] OR “Depression”[Mesh] OR (((depress* [Title/Abstract] OR distress [Title/Abstract]) OR (“Psychological Distress”[Mesh])) OR (“Depressive Disorder”[Mesh] OR “Long-Term Synaptic Depression”[Mesh] OR “Depression, Postpartum”[Mesh] OR “Depressive Disorder, Treatment-Resistant”[Mesh] OR “Bipolar Disorder”[Mesh] OR “Dysthymic Disorder”[Mesh] OR “Seasonal Affective Disorder”[Mesh] OR “Depressive Disorder, Major”[Mesh] OR “Adjustment Disorders”[Mesh] OR “Affective Disorders, Psychotic”[Mesh] OR “Depression”[Mesh])
(“Adult” [Mesh] or (adult*[Title/Abstract]) or (old [Title/Abstract]) NOT (“Child “ [Mesh] or (Child*[Title/Abstract])) NOT (“Adolescent “ [Mesh] or Adolescen* [Title/Abstract] OR Teen*[Title/Abstract] OR Youth [Title/Abstract] OR underage [Title/Abstract])
((“systematic review”[Title] OR “meta-analysis” [Title] OR meta [Title] OR systematic [Title]) OR (“Meta-Analysis” [Publication Type] OR “Meta-Analysis as Topic”[Mesh])) OR (“Systematic Review” [Publication Type] OR “Systematic Reviews as Topic”[Mesh])
The following Chinese electric databases will be searched: Chinese National Knowledge Infrastructure, CNKI (https://new.wanfangdata.com.cn/index.html) Database for Chinese Technical Periodicals, VIP (http://www.tydata.com/)
Below, the search strategy for CNKI is provided:
篇关摘= 成人 + 成年人 + 大学生 Not 篇关摘= 儿童 + 青少年 + 未成年 + 少年
篇关摘= 抑郁 + 心理
篇关摘= 系统评价 + 元分析 + 荟萃分析 + meta分析
Searching other resources
We will consult the following sources of grey literature and search websites of organizations for mental health research to identify relevant unpublished studies and reports. The following grey literature resources will be searched using the keyword “depression”: World Health Organization (https://www.who.int/) American Psychological Association (https://www.apa.org/) Centers for Disease Control and Prevention (https://www.cdc.gov/) National Institute of Mental Health (https://www.nimh.nih.gov/) Open Grey (http://www.opengrey.eu/)
In addition, we will also survey Google Scholar using the keyword “depression intervention” and scan the first 50 pages for relevant studies. Moreover, relevant reviews cited in previous systematic reviews on depression will be scanned, and reference lists of included studies will also be searched.
Analysis and presentation
Unit of analyses
Each entry in the map will be a systematic review of effectiveness. If a review contains multiple interventions, the reviewers will extract all data as dependent reports that are eligible for this EGM. The final EGM will identify the number of studies covered by the map in each sector or subsector.
Report structure
The EGM report will include the following sections: executive summary, background, intervention, results, and conclusion. The executive summary will summarize the report, providing key findings and implications for future policy planning and research. The background of this study will comprehensively describe the current situation of depressive disorder in adults and its impact on society. Examples of existing interventions are described and the goals of EGM are clarified. In addition, we will describe the scope by defining an intervention and outcome framework.
The description of the methods will include a definition of the data sources and methods of searching, the inclusion and exclusion criteria, study selection, study confidence appraisal, data extraction methods, and the approach to presentation/visualization. This section will provide a table in the text showing one full search from a database and a PRISMA flow chart. An appendix will provide full search strategies used for each database, including any restrictions and filters used.
The outcome will show the number, type, and quality of the studies retrieved for the outcome categories, the population targeted for the specific study, and the change in outcomes after the intervention.
The conclusion is expected to provide insights for researchers and decision-makers, build on the evidence base in this field, and identify key areas for future research. Moreover, we will include studies considering the impact of conducting EGM.
The following tables and figures will be included: Figure: PRISMA flow chart table. Table: Number of studies by intervention and subcategories. Table: Number of studies by population. Table: Number of studies by intervention category and study confidence.
Filters for presentation
We will present results as a matrix of interventions (rows) and outcomes (columns) and assess the availability of evidence across the additional filters. In addition to the interventions and outcomes, the following filters will be coded (details are in Tables 7 and 8): Population subgroups of interest include age group (young and middle-aged adults: 18–60 years; older adults: 60 years and above), gender and sexual orientation (female, male, and LGBT community), career (e.g., nurse, doctor, student, teacher, police), and health state (depression alone, depression with physical disease, and depression with other psychical disorders). The number of interventions: single treatment and combination treatment. Type of depression: disruptive mood dysregulation disorder, major depressive disorder, persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, substance or medication-included depressive disorder, depressive disorder due to another medical condition, bipolar depression, other specific depressive symptoms, unspecified depressive disorder. The severity of depression: mild depressive symptoms, moderate depressive symptoms, moderate to severe depressive symptoms, severe depressive symptoms, major depressive symptoms, other specific depressive symptoms, and undefined. Period of depression: lifetime, 12 months, 6 months, 1 month, and not stated. Number of episodes: depression episode, depression recurrence, and not stated; The implementer of treatment: self-help, healthcare provided, and provided by mental health professionals or volunteers. Effectiveness of interventions: We will record whether the systematic review reported a mean positive statistically significant effect, a mean statistically significant negative effect, or no statistically significant difference between treatment and comparison conditions. Region: Africa, Americas, East Asia, Europe, Eastern Mediterranean, Western Pacific. Countries: any noted. Conflict of interest: yes, no, and unclear. Quality of studies: high, moderate, low, and critically low.
List of filters.
Continue: List of filters.
Dependency
Each entry in the map will be a systematic review of effectiveness. The final EGM will identify the number of studies covered by the map in each sector or subsector.
Data collection and analysis
Screening and study selection
Two reviewers (Ren JJ and Huang XY) will independently screen the titles and abstracts of all retrieved articles. Furthermore, titles and abstracts will be screened by Rayyan based on population, intervention, and study design but not the outcome (Ouzzani, 2016). Full texts of potentially eligible studies will then be retrieved and screened in Excel. The reviewers will compare the results, and conflicts will be resolved through discussion or by a third reviewer (Xu Z). Authors of studies or reviews are not contacted for missing information.
Data extraction and management
Coding is the process of capturing the required data from included studies, such as study population, intervention, and study design. Coding will be done independently by two coders (Li JY and Xu Z) using EPPI Mapper, with a third-party arbitrator (Guo LP) in the event of disagreement. The studies will be coded based on intervention category and sub-category, indicator/outcome domain, and sub-domain; treatment population, country, and population characteristics. In addition, coding includes critical appraisal, which is described in Section 3.5. Guo LP will be responsible for data management.
Tools for assessing the risk of bias/study quality of included reviews
The reliability of the study findings in the included systematic reviews will be assessed using a measurement tool to assess systematic reviews (AMSTAR-2). This progress will be conducted independently by two reviewers (Li JY and Xu Z), with any disagreements will be resolved by a third reviewer (Yang KH). The items of AMSTAR-2 are shown in Table 9 (Shea, 2017).
Items of AMSTAR-2.
Methods for mapping
We will use the EPPI Mapper mapping tool developed by the EPPI-Centre to display identified studies using the framework described above.
Footnotes
ACKNOWLEDGMENTS
This study is supported by funding of the Major Project of the National Social Science Fund of China: Research on the Theoretical System, International Experience, and Chinese Path of Evidence-based Social Science (Project No. 19ZDA142), and the Natural Science Foundation of Ningxia (No. 2020AAC03123).
CONTRIBUTIONS OF AUTHORS
Zheng Xu is a teacher at the Psychological Counselling Centre of Lanzhou University. Kun Qiao is the deputy director of the Institute of Medical Physiology and Psychology at the School of Basic Medical Sciences of Lanzhou University. Wen Wang is an associate doctor of the psychiatry department of the First Hospital of Lanzhou University. Yaogeng Chen is a professor focused on the mental crisis at the School of Science at Ningxia Medical University.
All authors are experienced systematic reviewers, which means they are proficient in carrying out the various processes in a Systematic Review, such as eligibility screening, quality assessment, and coding. Kehu Yang is the director of the Evidence-based Social Sciences Laboratory at Lanzhou University and the author of several Chinese evidence-based textbooks.
Howard White is the lead adviser on evidence mapping and the second coauthor. He has authored a paper on mapping methods used by different agencies that assisted the development of Campbell guidelines and standards for Evidence and Gap Maps and is the author of published and ongoing maps, such as homelessness, disability, violence against children, and youth employment, including the first mega-map on child welfare and the map of maps in international development.
All authors have previous experience in developing search strategies.
Screening, coding, analysis, and writing will be led by Liping Guo. Overall supervision is provided by Kehu Yang and Howard White.
DECLARATIONS OF INTEREST
All authors (GLP, LJY, XZ, YKH, RJJ, HXY, CYG, and HW) declared no conflict of interest.
SOURCES OF SUPPORT
Research on the Theoretical System, International Experience, and Chinese Path of Evidence-based Social Science, China Natural Science Foundation of Ningxia
The Major Project of the National Social Science Fund of China
None
References
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