1. Introduction
Postpartum depression (PPD) is a subtype of depressive disorder affecting a large number of women immediately after childbirth which could seriously compromise both mother and newborn’s health [
1,
2].
Around 60-80% of new mothers experience “baby blues” few days after delivery, a condition characterized by feelings of sadness, loneliness, worthlessness, restlessness, and anxiety which usually resolve within the first two weeks [
3,
4]. This temporary discomfort, characterized by unstable mood and crying crisis, is caused by the rapid hormonal and psychic adaptation processes happening the first weeks after childbirth. Sometimes these feelings persist for a longer period, leading to psychic fragility, stress and anxiety [
5]. PPD is a long-lasting depressive disorder that occurs 4-6 weeks after childbirth in which women experience depressed mood, loss of interest and pleasure, loss of confidence and self-esteem, excessive guilt, difficulty concentrating, sleep and appetite disturbances [
6]. The prevalence of PPD is around 10-20%, even if it varies according to different cultures and income levels of studied countries [
7].
Generally, women are subjected to many biological variations after delivery, such as altered levels of sexual hormones (oestrogen and progesterone), lactogenic hormones (oxytocin and prolactin) and increased amount of stress hormones (e.g., cortisol), correlated with a dysregulation in the hypothalamic–pituitary–adrenal (HPA) axis [
8]. However, these hormonal imbalances lead to the depression onset only for women with a predisposition for mood disorders [
9]. Other factors playing a role in physiological changes after childbirth are neurotransmission dysfunction (i.e., γ-aminobutyric acid or GABA and glutamate) and monoamine (i.e., serotonin and dopamine) [
10]. Common changes in the mother’s normal daily routine, such as sleep disturbances and alteration of appetite, could lead to diurnal variations in mood, loss of concentration, and irritability, which altogether are possible cause of PPD development [
7].
Another recurrent feeling that women might experience in the first trimester after delivery is the sense of guilt, arising from the difficulty to look after their baby. Even though this emotion has a serious impact on both mother and child’s lives, it is very often underestimated and it is not reported by women because of the fear to be labelled as "bad mothers” [
11].
The first six months after birth have a pivotal role in child’s physical and psychological development. For this reason, PPD can have serious consequences on the baby. Uncertain affection, reduced psychomotor and cognitive development are just some of the possible effects, which can globally affect the infant’s development, especially in terms of intelligence and language learning ability [
1,
12]. One of the most important leading consequence of women’s depressive mood after delivery is the difficulty in lactation [
13]. Breastfeeding is of paramount importance both for the newborn’s optimal immune system development, and for the mother’s health, since it reduces type 2 diabetes, cardiovascular risk, and breast and ovarian cancer development [
14,
15]. Sometimes lactation could cause mastitis, an inflammation of breast tissue, usually followed by infection. It is a common and debilitating disease which often comes with the cessation of exclusive breastfeeding. Mastitis and breast abscesses are usually associated with the pathogens
Staphylococcus aureus,
Staphylococcus epidermidis and some members of
Corynebacteria that are known to produce biofilms and show multidrug resistance. For these reasons, antibiotic treatment is frequently ineffective, causing in many cases breastfeeding cessation [
16,
17,
18].
Nowadays, PPD current best practices involve pharmacological interventions, cognitive therapy, psychological support and, in worst cases, hospitalization [
19]. Thus, the development of non-invasive and non-harmful treatments to support new-mothers’ health is eagerly required.
In this scenario, probiotics have been extensively studied due to their ability to improve gut microbiota (GM) and eubiosis. Indeed, such microorganisms affect host’s health, influencing both the gastro-intestinal and the immune system [
20,
21]. Bacteria living in the gut are also able to modulate the brain functions through a bi-directional communication pathway, named “gut-brain axis” [
22]. Such pathway includes neuroendocrine secretions, short-chain fatty acid production and autonomic nervous system stimulation [
23]. Consequently, intestinal dysbiosis can be associated to a wide range of psychological problems, including neuropsychiatric disorders, depression, and anxiety, that are characterized by increased levels of pro-inflammatory cytokines and oxidative stress [
24,
25]. Thus, an alteration of the intestinal microbial composition can affect the gut-brain communication, leading to the onset of depressive disorders [
26].
In vitro studies suggest that
Limosilactobacillus reuteri PBS072 and
Bifidobacterium breve BB077 can influence the endogenous production of GABA and serotonin and improve stress-related parameters. Following these promising results, two clinical trials have been carried-out in different target population, such as stressed students during exam session and employees in the early pandemic, showing an improvement in cognitive functions, mood and sleep quality [
27,
28].
The primary aim of the present study was to determine if a probiotic supplement containing Limosilactobacillus reuteri PBS072 and Bifidobacterium breve BB077 could improve new mothers’ psychological and physical well-being by reducing the risk of developing PPD, through the modulation of the gut-brain-axis. As a secondary outcome, self-confidence and breastfeeding ease were evaluated as a marker of mothers’ mental state in the post-partum period. Indeed, these two outcomes are related to lactation performance, decreasing excessive baby crying and reducing the production of intestinal gas (i.e. infant colic), due to a relaxed attitude of the new mothers.
4. Discussion
According to the World Health Organization, stress has been defined as the “Health Epidemic of the 21st Century”. Indeed, the physical and psychological burden caused by long stress period is increasing [
33]. Stressful situation can affect quality of sleep, provoking fatigue, irritability, and concentration difficulties. Moreover, stress may lead to intestinal dysbiosis and modify the GM, and consequently the gut-brain communication. Therefore, keeping a balanced gut-microbiota through probiotic supplementation could be a valid solution to achieve an effective gut-brain crosstalk, resulting in an improvement of mental conditions, as reported by previous studies [
22,
34,
35]. Studies on animal models of depression reveal that GM in depressed mice changes significantly from healthy subjects. Indeed, GM modulates neuro-inflammatory activity in the hippocampus through a dysfunctional microbiota-gut-brain axis, leading to anxiety- and depression-like phenotypes [
36]. Similarly, a study revealed that fecal microbiota transplantation (FMT) from human patients with major depressive disorder (MDD) into rats could induce a depressive-like phenotype in the recipient animals [
37]. Rats receiving the FMT from depressed humans showed significantly higher immobility and less struggling in the forced swim test than rats receiving FMT from healthy human donors, a behavior interpreted as depressive phenotype. Furthermore, the former group showed an altered intestinal tight junction gene expression compared to animals receiving FTM from healthy donors [
37]. These data highlight the key role of microbiota in modulating depression.
Nowadays, it is well-known that probiotics supplementation in women at the last trimester of gestation and breastfeeding shape newborns’ immune system. According to the 2015 World Allergy Organization guidelines, pregnant women whose infants are at high risk for allergy should assume probiotics as a preventive treatment. Indeed, probiotic integration positively stimulates the children’s immune system, decreasing in the onset of allergic diseases [
38].
The majority of scientific studies available in literature evaluating the immune system response and the GM composition of new-born babies involve women taking probiotic supplements, especially during the perinatal period [
39]. Thus, the effect of probiotic supplementation both during pregnancy and in the puerperium have been rarely assessed. Indeed, in the puerperium, mothers experience several physiological changes that could lead to stress and anxiety. Progesterone and estrogen, two hormones increasing tenfold during pregnancy, dramatically drop after the delivery. This condition could persist for 3-4 weeks and it is related to many changes in the mother’s life, such as diurnal variations in mood, poor concentration, and irritability [
7]. Usually this condition self-resolves without any intervention, but sometimes these mental states could last longer, leading to more serious discomforts, such as PPD [
5].
The aim of our study was to assess if a supplement containing Limosilactobacillus reuteri PBS072 and Bifidobacterium breve BB077 plus multivitamins may provide a safe support to new mothers after delivery, especially improving their mental state. Indeed, we observed the effect on mood of two probiotic strains administered to mothers immediately after delivery, in order to prevent the onset of depressive and anxious symptoms linked to PPD development, together with the indirect influence of the probiotic intake on new-born during the first trimester.
The evidence that women supplemented with probiotics had fewer symptoms of postnatal anxiety and depression caused by stress is consistent with two previous clinical studies evaluating the effect of probiotics on stress-related parameters in different target populations. The first study is a proof-of-concept trial of 30 students enrolled during exam session and treated with a probiotic supplement containing the same strains
L. reuteri PBS072 and
B. breve BB077. Results show an improvement in their cognitive function and sleep quality [
27]. In the second study, Nobile et al. reported the improvement of the general mood state, anger, and tension feelings, as well as sleep quality, in employees administered with the same probiotic blend during pandemic lockdown, suggesting their potential role in the management of work-related stress [
28].
According to these preliminary evidence, our study was designed to assess the effect of probiotics on mood and mental state in the period in which first PPD symptoms emerge. It is worth to notice that the clinical protocol could not include evaluation questionnaires at T0 since they are not relevant before the occurring of different and opposite emotional events (e.g., excitement and joy up to weakness and frightening due to motherhood). However, this study demonstrated a significant improvement of mothers’ mood in the first trimester when supplemented with
Limosilactobacillus reuteri PBS072,
Bifidobacterium breve BB077, and vitamins compared to the control group in accordance to the EPDS questionnaire (26% at T1 and 35% at T2, respectively). In addition, the probiotic group at T1 resulted in a total score underneath the threshold of minor depression, while the control group reached a mean value of 12, which is interpreted as “fairly high possibility of depression” on the EPDS [
30]. On the same way, this study demonstrated a significant improvement in breastfeeding quality in the probiotic group in accordance to the BSES-SF (20% at T1 and 24% at T2, respectively). This questionnaire is associated with the self-confidence during breastfeeding, assessed as lactation performance in new-mothers.
Remarkably, this study showed a significant daily improvement in baby crying/fussing events (p<0.001), according to the BSES-SF questionnaire at both T1 and T2 for the probiotic group. A possible explanation could be that probiotics may ameliorate mother’s mood, who being less stressed and happier, may differently perceive the crying episodes of their children in terms of episodes’ number and severity. Also, it could be speculated that more self-confident and calm mothers positively influence baby’s behavior. A further potential explanation of this outcome is that crying events could be possibly linked to reduction of infant colic mediated by the indirect probiotic intake through breastfeeding [
40]. Scientific evidence correlates changes in the GM with colicky infants, thus the use of probiotics to counteract this disorder has rapidly increased in recent years, focusing on the reduction of crying time as a primary outcome [
41,
42,
43]. It is well known that bacteria present in the breast milk are transferred from the mother’s intestine to the mammary gland, and consequently from the mother milk to the infant gut [
39]. In this context, a balanced microbiota in the mother’s gut could influence the growth of the child’s resident bacterial population, preventing intestinal gases production. Therefore, probiotic assumption might reduce infant colic episodes, decreasing crying events and improving mother’s mood [
44].
To the best of our knowledge, only another published study assessed PPD neurological parameters as a result of the effect that probiotics in new mothers. This study investigated the effect of
Lactobacillus rhamnosus HN001 on postpartum depression and anxiety symptoms using EPDS and State Trait Anxiety Inventory (STAI) questionnaires [
34]. Slykerman and colleagues studied the oral intake of a probiotic supplement throughout the entire perinatal period, up to 6 months from delivery. The data of this study were collected retrospectively the occurring of the events (up to 6 months later). Due to the latency between the effective occurring event and its registration, this design could be a limitation of the study since mothers could have not remembered correctly the events throughout the long administration/ observational period.
In our study, the questionnaires used for the assessment of mothers’ mood state and breastfeeding confidence lack of the basal score, as selected questionnaires only refer to post-natal period; indeed, they could not be properly filled at T0 since mothers have just undergone delivery, without experiencing the wide range of emotional events linked to motherhood yet. For this reason, no evaluation was performed at T0 in order to avoid any alteration of the EPDS and BSES-EF questionnaires.
As secondary outcome, mastitis incidence was taken into consideration to further characterize the lactation performance. However, since the two items of BSES-SF questionnaire related to mastitis did not record any episodes, this outcome was not considered.