Exploring the Association Between Stress and the Experience of the Milk Ejection Reflex: A Scoping Review Protocol

Abstract

Background:

The impact of stress exposure on the experience of the human milk ejection reflex in lactation has largely been neglected within the literature. Animal studies suggest an inhibiting effect on milk release, although applicability of these findings to the human mammary gland is limited due to species-specific variation in both lactation physiology and stress response pathways. Incidental findings regarding the newly identified condition of dysphoric milk ejection reflex present the possibility that the release of human milk is heavily dependent upon a robust stress response system.

Research Aim:

The primary aim of this scoping review protocol is to provide a transparent method for the mapping of existing evidence related to stress exposure and the experience of the milk ejection reflex in human lactation. Within this, a secondary aim will be to outline an approach to collate extant literature on stress and the experience of dysphoric milk ejection reflex and determine whether there is a stress-related aetiology to the condition.

Methods:

This protocol is informed by an established five-stage framework for conducting scoping reviews, supporting the identification and selection of relevant studies. Qualitative data will be reflexively thematically analysed, while quantitative data will be extracted and summarised in diagrammatic form.

Discussion:

This scoping review protocol addresses a significant knowledge gap in human lactation by outlining an approach to investigating stress and the experience of the human milk ejection reflex in lactation, while advancing understanding of dysphoric milk ejection reflex.

Keywords

breastfeeding cortisol dysphoric milk ejection reflex (D-MER)hypothalamic–pituitary–adrenal axis maternal health milk ejection reflex stress

Introduction

It is well established that exclusive breastfeeding (EBF) is the optimal source of nutrition for the infant during the first 6 months of life (Patnode et al., 2025), conferring extensive, long-term health benefits that remain unparalleled by commercial milk formulas (CMFs). EBF refers to the sole provision of human milk for the infant’s sustenance with no other food or drink provided, except for rehydration solutions (ORS), vitamins, minerals, and medicines where required (World Health Organization [WHO], 2025a).

From gut maturation (Naspolini et al., 2025) to immunological refinement (Lokossou et al., 2022) and beyond, human milk has long been recognised by the WHO (2023) as the ultimate first foodstuff, tailored to meet the complex, multi-system needs of the developing baby.

For the lactating mother, the recommended period of exclusive breastfeeding (EBF) can act as a safeguard against several serious disease trajectories including gynaecological cancers, type 2 diabetes mellitus and osteoporosis (Mustafa et al., 2024).

A growing body of evidence also documents the psychological benefits of EBF, which include improved maternal mood state (Biagianti & Gripsrud, 2024) and reduced stress reactivity (Brunton et al., 2008; Simon et al., 2016) in the postnatal period. This time represents a critical juncture in maternal mental health, wherein everyday stressors are compounded by the demands of new motherhood (E. Q. Cox et al., 2015).

According to the Maternal Mental Health Alliance, suicide remains the leading cause of death among new mothers between 6 weeks and 12 months following childbirth (Tubb, 2025) and there is a significant increase in the incidence of mental illness in this cohort (Reinsperger et al., 2025). In recognition of EBF’s protective effects, it is crucial that mothers feel well supported to overcome any barriers to breastfeeding, so that they may then accrue the health benefits.

Dysphoric milk ejection reflex (D-MER) is one such challenge for which there is currently a lack of awareness and support, and although this is partly due to its relatively recent identification, the limited pool of studies concerning the human milk ejection reflex (MER) as opposed to animal studies has no doubt stymied progress in the understanding of this newfound condition of milk let-down.

Ordinarily, the MER is accompanied by soothing sensations as a result of the release of nonapeptide oxytocin (OT). However, with D-MER the opposite appears true in that the release of human milk is accompanied by intense waves of negative valence (Cappenberg et al., 2025; Ureño et al., 2019), which can be categorised on three levels: affective, sensory, and cognitive.

In terms of the affective dimension, D-MER has been reported to emerge as a feeling of immense dread (McGuinness & Frawley, 2025), sadness (Deif et al., 2021), homesickness (Heise & Wiessinger, 2011), disgust and despair (Winchester, 2020), and anxiety (McGuinness & Frawley, 2025).

The sensory elements of the condition relate to a loss of appetite or extreme thirst (Uvnäs-Moberg & Kendall-Tackett, 2018), heart palpitations (McGuinness & Frawley, 2025), a hollow feeling in the pit of the stomach (Middleton et al., 2025), and nausea (Kacır et al., 2024).

Frustration and irritability (Cappenberg et al., 2025), suicidal ideation (Heise & Wiessinger, 2011), and a reduction in maternal self-efficacy (Žutić et al., 2025) constitute the cognitive aspects of the condition.

Incidental findings from research to date suggest a role for stress in the onset and presentation of the condition (Cappenberg et al., 2025; Kacır et al., 2024) and, given the maternal adaptations which take place to the stress response system in the perinatal period, there is reason to critically review this tentative relationship further. Following an initial search of the literature, the aims of the planned scoping review have been identified as:

Aim 1: Map existing evidence and knowledge gaps related to stress exposure and impact on the milk ejection reflex in human lactation.

Aim 2: Collate extant literature on stress exposure and presentation of dysphoric milk ejection reflex, to investigate whether there is a stress-related aetiology to the condition.

Key Messages

The limited knowledge related to the impact of stress exposure on the release of human milk has hindered understanding of newly identified condition of dysphoric milk ejection reflex.

The present scoping review protocol outlines a transparent and reproducible method in the investigation of stress exposure and its effects on the human milk ejection reflex.

These valuable insights could contribute towards heightened awareness, positive interventions and improved support for mothers experiencing challenges with the milk ejection reflex.

To focus the scoping review, the primary research question has been identified as:

RQ1: What empirical evidence exists regarding a relationship between stress exposure and the human milk ejection reflex?

The secondary research questions are:

RQ2: How is the concept of stress exposure operationalised within the literature related to the human milk ejection reflex?

RQ3: Are there identifiable differences in the effects of chronic and acute stressors in the onset and presentation of the dysphoric milk ejection reflex?

RQ4: To what extent are health-promoting, salutogenic approaches employed in the management of human milk ejection reflex difficulties?

Background

The Milk Ejection Reflex

The milk ejection reflex (MER) serves an indispensable role in lactation as the mechanism responsible for the expulsion of human milk from the nipple areola complex (NAC). Without the MER, the ability to breastfeed would be significantly compromised, obstructing the removal and flow of human milk to the suckling infant (Hartmann et al., 1994).

The two main hormonal drivers implicit in the production of human milk are polypeptide hormone prolactin (PRL) and nonapeptide oxytocin (OT) which is colloquially known as the “love hormone” due to its involvement in pair-bonding, reproduction, and affection (Magon & Kalra, 2011; Ng et al., 2023).

Whereas PRL stimulates mammary gland development and human milk production, the pulsatile release of OT from the posterior pituitary gland is the primary agent underpinning the MER. Circulating maternal OT prompts contraction of myoepithelial cells surrounding the mammary alveoli, which then propels human milk through the lactiferous ducts towards the nipple (McNeilly et al., 1994).

Activation of the MER can be achieved by tactile stimulation in the form of infant touch or suckling, whereby the infant extracts the human milk via a process of suck-swallow-breathe (SSwB) and through the synchronised movements of the mandible, gums, and tongue (Elad et al., 2014). Similarly, hand expression or mechanical pumping may also trigger the MER (Alekseev & Ilyin, 2016).

Certain emotive, audiovisual cues have also been known to induce a type of Pavlovian milk release, whereby the sight or vocalisations of an infant, not necessarily related to the lactating mother, prompt the spontaneous onset of the MER (Skowrońska et al., 2022).

The MER can occur multiple times within a single breastfeeding session and, quite often, these are perceived by the mother, although in some cases the let-down of milk remains undetectable (Uvnäs-Moberg & Kendall-Tackett, 2018; Watkinson et al., 2016).

In those instances where MER is sensed by the mother, it is often described in terms of a sudden “tingling” or “rushing down” feeling. Simultaneously, OT exerts its anxiolytic, soporific effects on the maternal mood state, with the pleasurable feelings likened to a “milky mist” in the breastfeeding mother (Biagianti & Gripsrud, 2024).

Despite the apparent affiliation between the stress-reducing properties of the lactogenic hormones involved in the human MER, there has been minimal investigation into this tentative relationship.

Although animal studies attest to an inhibitory effect of stress on the functioning of the MER (Peña et al., 2023; Torner et al., 2002; Valdez et al., 2011), the applicability of these findings to the human mammary gland is limited. This is due to species-specific differences in the physiology of lactation (Capuco & Akers, 2009), as well as variations in stress response regulation related to primary glucocorticoids (Tablado et al., 2021).

In lactating women, the body’s stress response system of the hypothalamic–pituitary–adrenal (HPA) axis undergoes extensive maternal adaptations which dampen stress reactivity (Brunton et al., 2008; Simon et al., 2016), fostering a calmer mental state and minimising the risk of disruption to the breastfeeding relationship (Simon et al., 2016).

Vital and life-sustaining modifications include a steady increase in the secretion of cortisol (CORT), a glucocorticoid hormone that is produced by the adrenal glands and supports restoration of the body to homeostasis following an acute episode of stress (Matyas et al., 2024). Circulating levels are tripled in the final stages of pregnancy (Jung et al., 2011) and this adaptation supports foetal lung, thyroid and gastrointestinal growth in utero (Garbrecht et al., 2006).

During breastfeeding, CORT production is inhibited by the pulsatile release of OT which imparts a stress-reducing effect on the mother-infant dyad. For this reason, CORT levels are found to be lowered in the immediate period following a breastfeeding session (Beery et al., 2023). Given CORT’s status as the gold-standard biomarker in the assessment of individual stress profiles (Ahmed et al., 2024b), it has been suggested that concentrations measured in human milk may reflect the maternal stress state (Neelon et al., 2015).

These findings support a growing body of evidence which highlight a bi-directional relationship between stress and breastfeeding more generally, with positive implications for maternal mental health and well-being where the mother feels adequately supported and relaxed (Biagianti & Gripsrud, 2024; Modak et al., 2023).

Breastfeeding is a learned skill, with mothers drawing upon a toolkit of resources to overcome the challenges and pitfalls that are commonly associated with the establishment and maintenance of lactation (O’Brien et al., 2009). The gap in the literature related to stress and the MER represents a significant shortcoming in our knowledge of human lactation that may have also hindered understanding of the newly identified condition, D-MER.

Dysphoric Milk Ejection Reflex

D-MER introduces a new window of enquiry into the relationship between stress and the milk let-down. First labelled by lactation consultant Alia Macrina Heise in 2007 (S. Cox, 2010), understanding of the condition is progressing, but is still in its early stages. There have been calls to advance the limited knowledge base (Ahmed et al., 2024a), and to build upon initial studies which have established preliminary characteristics of the condition.

Primarily, D-MER presents as intense waves of negative affect in the breastfeeding mother, which can last up to 5 minutes before and during the MER, occurring multiple times throughout a breastfeeding session (Cappenberg et al., 2025; Ureño et al., 2019).

The estimated prevalence rate varies from 5.9% (Žutić et al., 2025) to 15.4% (Moriyama et al., 2024), tentatively making this condition as common in the breastfeeding population as the more widely recognised challenge of mastitis (Wilson et al., 2020).

Reported symptoms include momentary feelings of immense sadness, overwhelming anxiety and panic, a hollow feeling in the stomach, and nausea (Heise & Wiessinger, 2011; Ureño et al., 2019).

In some instances, D-MER triggers co-morbid mental health disturbance in the affected individual, in the form of reduced maternal self-efficacy and suicidal ideation (Heise & Wiessinger, 2011). D-MER has also been found to contribute to the premature discontinuation of breastfeeding in around half of affected mothers (Žutić et al., 2025).

D-MER is often misdiagnosed as postnatal depression, most likely due to the shared characteristic symptom of low mood experienced within the postnatal period (Deif et al., 2021; Liu et al., 2023). This could have significant implications for treatment pathways and medical interventions, with reports that Norepinephrine-dopamine reuptake inhibitors (NDRIs), such as bupropion, have been prescribed without prior clinical testing or approval (Kacır et al., 2024).

Of interest to this scoping review protocol, are those incidental findings which suggest a potential stress-related aetiology to the condition which have not yet been fully articulated within the empirical literature.

In a recent cross-sectional study of lactating women, 62.1% of participants in the D-MER cohort reported that their stress levels corresponded with the severity of symptoms (Cappenberg et al., 2025).

Elsewhere, Kacır et al. (2024) reflected on whether D-MER was the by-product of a mis-wired “fight or flight response” in reference to the body’s stress response system. In the same study, women with D-MER exhibited higher scores on a psychometric measure of stress, when compared to mothers who did not experience D-MER. However, it is not clear whether reported stress levels were due to the adversity of breastfeeding with D-MER itself, or exogenous factors.

The aetiology of D-MER is unknown, with the prevailing theory suggesting that an atypical decrease in levels of the catecholamine neurotransmitter dopamine during milk secretion is responsible for the sudden, low mood experienced (Deif et al., 2021; Skowrońska et al., 2022). However, there is currently a lack of empirical evidence to substantiate this view, with reference often made to a single case study (Heise & Wiessinger, 2011). An additional aim of the planned scoping review will be to explore whether evidence exists to suggest a stress-related aetiology of D-MER.

Defining Stress

Since its theoretical inception by Selye in 1936, the attempt to define “stress” remains an ambiguous yet notable endeavour. Originally described as the non-specific physiological response of the body to a given demand (Selye, 1936), there have been continued attempts to refine the concept.

The transactional model proposed by Lazarus (1993), further expanded upon Selye’s work, highlighting a central role for individual appraisal and coping abilities in the onset of stress. Stress has variably been positioned as a stimulus, an individual response, a transaction between the person and the environment (Wezyk et al., 2024), and, in terms of its duration, dependent upon the methodological and theoretical approach taken (Shahsavarani et al., 2015).

It has been observed that there is a general leaning towards an overly negative conceptualisation of stress, which is often synonymous with pathological trauma (Richter-Levin & Sandi, 2021). As a result, research has focused extensively on the deleterious effects of stress, with findings indicating an increased risk of disease (Leigh et al., 2023), shorter lifespan (McKay et al., 2020), and poorer mental health outcomes (McLoughlin et al., 2021) among affected individuals.

In response to this predominantly negative framing of stress in the literature, Richter-Levin and Sandi (2021) developed a hierarchical model of the stress response, to differentiate between arousing, stressful, and traumatic experiences, outlining criteria based on emotional reaction, induced plasticity, and individual capacity to cope with future exposure to adversity.

This categorisation suggests that although both stress and trauma induce an immediate emotional/behavioural response, and long-term alterations in allostatic mechanisms, the changes provoked by stress are adaptive and do not necessarily lead to pathology.

For the purposes of this scoping review protocol therefore, stress is understood to be the individual’s psychophysiological reaction following exposure to a perceived adversity. This approach to the concept adheres to Richter-Levin and Sandi’s (2021) hierarchical framework, in that it is not characterised by the onset of the pathology typically observed in cases of trauma.

Justification for the Scoping Review

Despite the apparent association between maternal mood state and breastfeeding, the impact of stress exposure on the experience of the human MER has largely been neglected within the literature. Although a recent scoping review by Middleton et al. (2025) considered more broadly a spectrum of negative emotional experiences associated with the MER, this did not have an explicit focus on exposure to stress.

The precise nature of this relationship is not yet known, including how factors such as individual variability and stress duration (i.e., chronic vs. acute) influence the breastfeeding mother’s experience of the MER.

In part, this oversight stems from the historical pattern of generally delayed recognition for maternal health issues, due to a persistent androcentric bias in medical research (Merone et al., 2022). Reflecting this, the human milk ejection reflex was not empirically validated until 1943 (Newton & Newton, 1948; Waller, 1943).

In a similar vein, D-MER has yet to be afforded the formal status given to other specific disorders of lactation such as hypogalactia (092.4) and cracked nipples (092.1) within the International Classification of Diseases (WHO, 2019). A lack of awareness prolongs the risk of misdiagnosis, diminished support networks and treatment options for affected mothers (Deif et al., 2021; Liu et al., 2023).

D-MER is a critical component to consider within the remit of the scoping review protocol for two major reasons. First, D-MER undermines the notion that the hormones involved in the release of human milk are reliably stress-relieving for the mother. Second, the condition introduces the prospect that the human MER is heavily dependent on and intrinsically informed by a robust stress response system to ensure optimal functioning.

The results of the scoping review may have relevance for the development of therapeutic interventions and support strategies for those mothers who encounter challenges with the milk ejection reflex. Both the perceived quality and duration of breastfeeding can increase when mothers feel well-supported (Cook et al., 2021), making this research valuable in the context of the United Kingdom’s prevailingly low EBF rates (Office for Health Improvement and Disparities, 2025).

Methods

Design

This scoping review will employ Levac and colleagues’ (2010) iteration of the five-stage strategy pioneered by Arksey and O’Malley (2005), to inform each stage of the process. A scoping review can facilitate the operationalisation of key concepts and the refinement of hypothesis generation on a much broader scale than a systematic review. Therefore, a scoping review is the appropriate method to further determine the relationship between stress and the experience of the human MER. The full protocol is registered on the Open Science Framework (Identifier 532jt). The PRISMA-ScR checklist has been included to guide the reporting of this protocol and will inform the reporting of the final scoping review (see Appendix III).

Sample

Inclusion and exclusion criteria were developed in accordance with the 2024 Joanna Briggs Institute (JBI) model of population, concept and context (PCC; Aromataris et al., 2024) which promoted alignment with the research aims and questions of the scoping review (see Appendix II).

As the research is concerned with the association between stress and the experience of the MER in breastfeeding mothers, only studies with human participants will be included. Animal studies will be discounted, in recognition of the variation in underlying primary glucocorticoids involved in the stress response and lactation (Joëls et al., 2018) compared to humans, which would limit the extrapolation of findings.

Research with primiparous and/or multiparous mothers aged over 18 years, of uncomplicated, singleton gestation at full term (37–42 weeks) will be included. Participants must be actively (a) exclusively breastfeeding or (b) breastfeeding while/following successful weaning of the infant onto solid foods at any point during the postpartum period.

Studies where mothers express human milk for either bottle-feeding of their own infant, or for the purpose of donation, will also be included in the study as electric or manual pumping of human milk still stimulates the MER by mimicking the action of infant suckling.

Works that primarily concern commercial milk formula (CMF) feeding, weaning from EBF to formula milk or mixed feeding comprised of both breastfeeding and formula milk will also be excluded, as the inclusion of CMF could impact the effects of stress on the experience of the MER. Studies which integrate both breastfeeding and other modes of infant feeding for the purposes of comparison, for example, effects of stress between breastfeeding and CMF feeding mothers, will be included.

Literature with an overarching focus on trauma and exposure to adverse events in the perinatal period will form part of the exclusion criteria. This would encompass birth trauma, pregnancy loss, unplanned and emergency interventions during childbirth, diagnosis of terminal illness, receiving palliative care, PTSD, postpartum psychosis, and postnatal depression.

Exclusion criteria extend to literature concerned with inducing lactation, in acknowledgement that pharmacological interventions may impact outcomes related to stress and the experience of the MER which cannot be fully addressed within the remit of the current scoping review.

Studies with a primary focus on severe trauma and stress-related pathology in the perinatal period will be excluded from the subsequent scoping review, as these diagnoses would indicate an extreme manifestation of stress (Ayers & Ford, 2016). Additionally, research with a focus on DSM-5-TR diagnoses (American Psychiatric Association, 2022), including PTSD, acute stress disorder, prolonged grief disorder, and adjustment disorders, will be excluded from the search.

In acknowledgement of the varying measures employed to assess psychophysiological aspects of stress, studies which utilise quantitative (e.g., psychometric or biologic) and/or qualitative (e.g., interviews, case studies, clinical reports) or mixed methods assessments will be incorporated into the search.

Search Strategy and Data Collection

The search strategy was developed in collaboration with the faculty subject librarian, and key terminology was refined to achieve optimal results by incorporating both Boolean operators, relevant Medical Subject Headings (MeSH), truncation and phrase-searching where appropriate (see Appendix I).

The title, abstract, and article key words of the following electronic databases will be searched, capturing empirical literature of peer-reviewed and non-peer-reviewed primary studies and grey literature such as Doctoral and Master’s theses and clinical reports: CINAHL Ultimate, SCOPUS, LILACS, APA PsycInfo, and PubMed.

To avoid duplication and retain focus on primary studies which make original contributions to the knowledge base, literature reviews in all forms, including systematic, narrative, meta-analysis, and traditional, will also be excluded during the screening phase. Non-empirical articles such as commentaries, editorials, correspondence, web content such as blog and social media posts, perspective/opinion pieces, and conference abstracts will also be excluded for the same purpose.

Hand-searching of key journals and citations will be conducted simultaneously. A preliminary pilot search using the key terms and approach identified confirmed that the research subject is viable for the purposes of the scoping review.

The date range for studies to be included is January 2000 to August 2025, with the former representing the advent of a renewed interest in breastfeeding research and infant feeding trends (Renfrew et al., 2012; Wright & Schanler, 2001).

To capture a diversity of sociocultural perspectives from within the extant literature, the search strategy is not limited to a specific geographical location, although included studies will be in English. This is due to time and logistical constraints regarding acquiring the additional resources that would be required for translation, coupled with a need to reduce the risk of misinterpretation.

Data Management, Collection, and Extraction

Selected sources will be subject to an iterative process of extraction, analysis, and synthesis. Citations retrieved from the databases will be imported into desktop reference management software Mendeley and compiled using Microsoft Excel to support the data extraction and screening process, filtering and removing duplicates and entries which meet the exclusion criteria.

A summary table form of metadata will be created in Excel which will include information on author(s), year of publication, title, country of study, language, publication source title, type of evidence source, abstract, research aims, methodology, method details, population, sample size, study sample description, limitations of study/knowledge gaps, and summary of results and main findings pertaining to RQ1–RQ4.

Data Synthesis and Analysis

In this concluding stage of the scoping review, the main findings from the included studies will be reported in narrative form. A reflexive thematic analysis of the evidence will then be conducted in accordance with Braun and Clarke’s (2019) six-phase process, assessing and identifying overarching findings in relation to the research questions.

Quantitative data will be presented in diagrammatic form, providing both descriptive information and highlighting key trends of the association between stress and the experience of the MER. Examples of variables to be presented in summary form include: study characteristics, intervention/exposure, outcome measure, types of data, and reported values.

Discussion

The purpose of this scoping review protocol has been to outline a transparent and reproducible method for the comprehensive mapping of extant literature related to the impact of stress on the experience of the human MER. Oversight of this topic has subsequently led to knowledge gaps in the understanding of the newly identified condition of D-MER, which appears to have a stress-related aetiology based on preliminary findings.

A scoping review is an appropriate method to investigate a subject that has received limited attention within the literature. A critical aim of this scoping review protocol is to develop a pathway towards a broader understanding of the phenomenon of interest and address the central research questions, by capturing relevant multidisciplinary sources of information.

The main strength of this protocol is that it aims to address a major knowledge gap within the literature that has real-world consequences for affected women. Namely that the lack of empirical investigation into stress and the human milk ejection reflex may have hindered understanding of the newly identified breastfeeding condition of dysphoric milk ejection reflex. As a result, women affected by D-MER are often met with unawareness, misdiagnosis, and general mismanagement of the condition (Deif et al., 2021; Liu et al., 2023). This omission is surprising given the enmeshment between lactogenic hormones and the maternal stress response system (Beery et al., 2023), an oversight that the planned scoping review aims to correct.

The integration of Arksey and O’Malley’s (2005) five stage framework with the addition of Levac and colleagues’ (2010) iteration allows for the broad mapping of the extant literature and enhances the methodological rigour of the review—which should ultimately provide fertile ground for future hypothesis generation.

In terms of limitations, this protocol did not integrate a quality assessment into the screening phase, which is an optional component of a scoping review, and this may impact the reliability of the findings. The inclusion/exclusion criteria related to language requirements may have significantly reduced the available pool of studies and may have introduced sociocultural, Western-centric bias through its preference for studies published in English. This is important to note given that a scoping review aims for breadth above all else. As a partial remedy to this, there were no restrictions on the geographical location of studies, and the Latin American and Caribbean Health Sciences Literature (LILACS) was incorporated as a key database within the scoping review protocol.

At present, there is no treatment pathway for D-MER and traditional support networks for affected mothers are diminished due to a general lack of awareness of the condition. It has been reported that D-MER has also contributed to lowered maternal self-efficacy, disruption to the breastfeeding relationship (Žutić et al., 2025) and, in some cases, suicidal ideation in lactating women with the condition (Heise & Wiessinger, 2011), making this issue a public health priority falling within the WHO’s (2025b) Sustainable Development Goals 2 and 3 of Zero Hunger and Good Health and Well-Being, respectively.

The MER serves as a vital function of breastfeeding for the mother-infant dyad. The planned scoping review will address a critical knowledge gap in how this mechanism is affected by stress, while simultaneously advancing insight into the aetiology and characteristics of D-MER.

Ultimately, this scoping review protocol aims to contribute towards an improved understanding of how to identify D-MER, which may help to mitigate the risk of misdiagnosis with other mood-related conditions which occur during the postnatal period.

Footnotes

Appendix

Appendix III.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) Checklist (Tricco et al., 2018).

SECTION	ITEM	PRISMA-ScR CHECKLIST ITEM	REPORTED ON PAGE N/A – See OSF full protocol (Identifier: 532jt)
TITLE
Title	1	Identify the report as a scoping review.	N/A
ABSTRACT
Structured summary	2	Provide a structured summary that includes (as applicable): background, objectives, eligibility criteria, sources of evidence, charting methods, results, and conclusions that relate to the review questions and objectives.	N/A
INTRODUCTION
Rationale	3	Describe the rationale for the review in the context of what is already known. Explain why the review questions/objectives lend themselves to a scoping review approach.	N/A
Objectives	4	Provide an explicit statement of the questions and objectives being addressed with reference to their key elements (e.g., population or participants, concepts, and context) or other relevant key elements used to conceptualize the review questions and/or objectives.	N/A
METHODS
Protocol and registration	5	Indicate whether a review protocol exists; state if and where it can be accessed (e.g., a Web address); and if available, provide registration information, including the registration number.	N/A
Eligibility criteria	6	Specify characteristics of the sources of evidence used as eligibility criteria (e.g., years considered, language, and publication status) and provide a rationale.	N/A
Information sources*	7	Describe all information sources in the search (e.g., databases with dates of coverage and contact with authors to identify additional sources), as well as the date the most recent search was executed.	N/A
Search	8	Present the full electronic search strategy for at least one database, including any limits used, such that it could be repeated.	N/A
Selection of sources of evidence^†	9	State the process for selecting sources of evidence (i.e., screening and eligibility) included in the scoping review.	N/A
Data charting process^‡	10	Describe the methods of charting data from the included sources of evidence (e.g., calibrated forms or forms that have been tested by the team before their use, and whether data charting was done independently or in duplicate) and any processes for obtaining and confirming data from investigators.	N/A
Data items	11	List and define all variables for which data were sought and any assumptions and simplifications made.	N/A
Critical appraisal of individual sources of evidence^§	12	If done, provide a rationale for conducting a critical appraisal of included sources of evidence; describe the methods used and how this information was used in any data synthesis (if appropriate).	N/A
Synthesis of results	13	Describe the methods of handling and summarizing the data that were charted.	N/A
RESULTS – N/A as relates to completed scoping review
Selection of sources of evidence	14	Give numbers of sources of evidence screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally using a flow diagram.	N/A
Characteristics of sources of evidence	15	For each source of evidence, present characteristics for which data were charted and provide the citations.	N/A
Critical appraisal within sources of evidence	16	If done, present data on critical appraisal of included sources of evidence (see Item 12).	N/A
Results of individual sources of evidence	17	For each included source of evidence, present the relevant data that were charted that relate to the review questions and objectives.	N/A
Synthesis of results	18	Summarize and/or present the charting results as they relate to the review questions and objectives.	N/A
DISCUSSION
Summary of evidence	19	Summarize the main results (including an overview of concepts, themes, and types of evidence available), link to the review questions and objectives, and consider the relevance to key groups.	N/A
Limitations	20	Discuss the limitations of the scoping review process.	N/A
Conclusions	21	Provide a general interpretation of the results with respect to the review questions and objectives, as well as potential implications and/or next steps.	N/A
FUNDING
Funding	22	Describe sources of funding for the included sources of evidence, as well as sources of funding for the scoping review. Describe the role of the funders of the scoping review.	N/A

Note. JBI = Joanna Briggs Institute; PRISMA-ScR = Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews.

Where sources of evidence (see second footnote) are compiled from, such as bibliographic databases, social media platforms, and Web sites.

†

A more inclusive/heterogeneous term used to account for the different types of evidence or data sources (e.g., quantitative and/or qualitative research, expert opinion, and policy documents) that may be eligible in a scoping review as opposed to only studies. This is not to be confused with information sources (see first footnote).

‡

The frameworks by Arksey and O’Malley (6) and Levac and colleagues (7) and the JBI guidance (4, 5) refer to the process of data extraction in a scoping review as data charting.

The process of systematically examining research evidence to assess its validity, results, and relevance before using it to inform a decision. This term is used for Items 12 and 19 instead of "risk of bias" (which is more applicable to systematic reviews of interventions) to include and acknowledge the various sources of evidence that may be used in a scoping review (e.g., quantitative and/or qualitative research, expert opinion, and policy document).

ORCID iDs

Jennah M. Evans

Richard Paul

Agata B. Wezyk

Dominique Mylod

Ethical Considerations

No Ethics Committee was needed for this scoping review protocol.

Author Contributions

Jennah M. Evans: Conceptualization; Data curation; Investigation; Methodology; Project administration; Writing – original draft.

Richard Paul: Conceptualization; Methodology; Supervision; Writing – review & editing.

Agata B. Wezyk: Conceptualization; Methodology; Supervision; Writing – review & editing.

Dominique Mylod: Conceptualization; Methodology; Supervision; Writing – review & editing.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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