Incidence and awareness of dysphoric milk ejection reflex (DMER)

Introduction

Lactation, which is strongly encouraged by the World Health Organization and obstetric and pediatric societal organizations, offers known benefits and is recommended for up to the first two years of life or longer [1]. Breastfeeding counseling should encompass its advantages and associated conditions.

One such condition that is understudied is Dysphoric Milk Ejection Reflex (DMER). It is characterized by the abrupt onset of transient negative emotions that occurs in select lactating women just before the milk ejection reflex and milk release [2], [3], [4] and may lead to early weaning [5]. Symptoms last between 2 and 3 min, resolving after milk letdown [6], and can include anxiety, sadness, panic, irritability, oversensitivity, agitation, and tearfulness [7]. Many may mistake DMER for postpartum depression [8].

DMER likely has a physiologic basis that may be influenced by environmental stressors and psychological context [6]. It has been hypothesized to involve several pathophysiological mechanisms, mainly centered around the hormones oxytocin and dopamine [8], 9]. Oxytocin normally facilitates milk ejection and promotes a calming effect. However, in DMER it may paradoxically upregulate the stress response [10]. Abnormal fluctuations in dopamine levels with increased prolactin levels during breastfeeding may mirror the transient DMER symptoms and is another hypothesis for the dysphoria [6], 10].

Limited information on DMER comes mostly from lay publications, including various breastfeeding websites and blogs. The minimal peer-reviewed literature on this condition likely reflects a lack of awareness about this topic within the medical community. It is important that providers recognize this condition, associated symptoms, and potential impacts for better diagnosis and differentiation from other postpartum and lactation conditions. Our primary objective was to determine the incidence of DMER. The secondary objectives were to describe symptom profiles and patient characteristics of DMER-positive patients and assess prior DMER familiarity.

Methods

This was a prospective observational study involving patients who initiated breastfeeding between December 2022 and May 2023 at two hospitals within a large healthcare system in New York. Additional inclusion criteria included willingness to fill out recurring surveys and English proficiency. This project was approved by the Northwell Health Human Research Protection Program and Institutional Review Board and complied with the World Medical Association Declaration of Helsinki regarding ethical conduct of research involving human subjects.

An established, validated instrument did not exist to address our objectives, so the study team designed an Initial Survey (Supplementary 1), containing items on breastfeeding goals and history and prior DMER familiarity, and a DMER Symptom Survey (Supplementary 2), assessing symptom presence, severity, and transiency (i.e. resolved within 5 min with a subsequent return to baseline). Listed symptoms included negative emotions, such as anxiety, depression, guilt, and impatience, mentioned previously in case reports/series and lay publications.

Breastfeeding patients were recruited by the primary author and lactation counselors on postpartum day 1–2, and they were given a brief introduction about DMER and how it may present. Upon consenting for study participation, participants were emailed a secure link with the Initial Survey, where they rated their prior DMER familiarity on a 5-point Likert scale of not at all to extremely familiar with DMER. They then received the DMER Symptoms Survey thrice daily for one week, where they subjectively rated symptom severity on a 5-point Likert scale of none to severe. Additionally, the surveys included a question addressing the transiency of these symptoms with a return to baseline mood (yes/no). Study data were collected and managed using Research Electronic Data Capture (REDCap) hosted at Northwell Health [11], 12]. REDCap is a secure, HIPAA-compliant, web-based system for managing online surveys and databases. Patient demographics and clinical history, including age, BMI, gestational age at delivery, mode of delivery, and NICU admission status were collected from medical records.

The primary outcome was DMER-positive status, as assessed on the daily DMER Symptoms Survey. There are no defined diagnostic criteria for DMER. For this study, we considered those DMER positive if they endorsed transient negative emotions or physical symptoms with a subsequent return to their baseline mood that recurred in ≥50 % of surveyed breastfeeding episodes. To meet this definition, at least 2 out of 2 surveys had to be positive, or a majority if 3 or more surveys were completed. The secondary outcomes were symptom severity and prior DMER familiarity.

Descriptive and clinical data were summarized with descriptive statistics. Basic inferential statistics were performed to examine relationships between variables using OpenEpi, Version 3, open-source calculator. A p value <0.05 was considered statistically significant.

Results

Out of 203 patients approached for participation, 151 consented, 1 withdrew, and 67 did not complete the Initial Survey or any DMER Symptoms Surveys and were not included in our analyses. The 78 people who filled out the DMER Symptoms Survey, averaging 6.9 surveys each (SD 6.5), were included in the primary analysis. The majority were married (79.5 %), nulliparous (56.4 %), and non-Hispanic white (57.7 %).

There were 538 completed DMER Symptoms Surveys, 168 of which were from those who screened positive for DMER. Those who screened positive averaged 8.0 surveys each (SD 5.1). The DMER incidence rate was 26.9 % (n=21). Symptom and severity profiles are listed in Table 1 and shown in Figure 1. All emotional and physical symptoms listed in the survey were endorsed by at least one individual, with a majority experiencing very mild agitation, annoyance, anxiety, frustration, guilt, and impatience.

Figure 1:

Symptom and severity profile among DMER positive participants. Patients could experience multiple symptoms and varying severity with each breastfeeding experience and when completing the surveys.

The majority of those who screened positive were <35 years old (71.4 %), non-Hispanic white self-identified race and ethnicity (52.4 %), married (72.7 %), and nulliparous (61.9 %), which was statistically similar to the DMER-negative group. DMER-positive participants were more likely to deliver via cesarean section than those who did not screen positive for DMER, 71.4 vs. 33.3 %, respectively (p<0.01). A minority had a history of anxiety/depression, preeclampsia, or a NICU admission, which was statistically similar to the DMER-negative group (Table 2).

Of those who completed the Initial Survey (n=55), 61.8 % (n=34) selected that they were unfamiliar with DMER, 29.1 % (n=16) selected they were slightly familiar, and 9.1 % (n=5) selected they were moderately familiar. No one selected that they were very or extremely familiar with DMER.

Among those who completed the Initial Survey, 28 (50.9 %) had previously breastfed, during which 8 (28.6 %) experienced DMER symptoms while breastfeeding previous children, and 3 (37.5 %) stopped breastfeeding because of DMER. Out of the 8 who reported prior DMER experience, 6 filled out the DMER Symptom Survey, and they all experienced a recurrence of DMER symptoms while breastfeeding their current infant.

Discussion

Our study is the first prospective study to evaluate DMER incidence and severity. Our small sample size limits robust conclusions and introduces bias. Restricting to English-proficient participants reduces generalizability. Also, we did not discern whether participants were feeding directly or pumping when completing the survey and could not comment on whether mode of lactation impacts symptom presence or severity. Nonetheless, we found that more than 1 in 4 lactating patients in our sample developed DMER, which is within the range of currently reported prevalence rates of 6.0–27.7 % [5], 7], 13], 14]. Since our participants were only surveyed during the first week postpartum, we may be underestimating the incidence rate, as symptoms may only initially present after the first week.

Most participants were unfamiliar with the condition. The gap between the higher number experiencing DMER and the lack awareness of the condition highlights the need for improved patient counseling and education, which begins with spreading awareness among healthcare providers. Fortunately, most patients experienced very mild symptoms, but we did not trend symptom severity beyond the first week postpartum. Given the importance of breastfeeding, and the recently updated recommendation by the World Health Organization to continue breastfeeding to 2 years of age, higher quality clinical research on this condition should better define, quantify, and qualify DMER to inform clinical practice and support successful breastfeeding relationships.