Children's anxiety symptoms and salivary immunoglobulin A: A mutual regulatory system?

Breast milk oxytocin and s-IgA modulate infant biomarkers and social engagement; The role of maternal anxiety

Breastfeeding has long been known to improve infants' health and mental development and to enhance the mother-infant bond, but much less research focused on the biological composition of breast milk and its associations with the infant's biomarkers and social development. In this exploratory study, we measured oxytocin (OT) and secretory immunoglobulin-A (s-IgA), the most abundant antibody in breast milk, and evaluated their associations with the same biomarkers in infant saliva and, consequently, with infant social engagement behavior. Fifty-five mother-infant dyads were home-visit and OT and s-IgA were assessed from breast milk and from infant saliva before and after a free-play interaction. Infant social behavior was coded offline using the Coding Interactive Behavior (CIB) and maternal anxiety self-reported. A path model revealed that mother's breast milk s-IgA impacted child social engagement via its links with child OT. In parallel, maternal breast milk OT was linked with infant social behavior through its association with the infant's immunity. This path was moderated by maternal anxiety; only in cases of high anxiety breast milk OT was positively connected to infant s-IgA. Our study, the first to measure OT and s-IgA in both breast milk and infant saliva in relation to observed social behavior, underscores the need for much further research on the dynamic interplay between breast milk composition, infant biomarkers, maternal mental health, and infant social outcomes. Results may suggest that biological systems in breast milk integrate to prepare infants to function in their social ecology through bio-behavioral feedback loops that signal the degree of stress in the environment.

Salivary secretory immunoglobulin A as a potential biomarker of psychosocial stress response during the first stages of life: A systematic review

Mucosal secretory immunoglobulin A (s-IgA) has been recognized as a key component of human first line defense against infection. However, its reactivity to psychosocial stressors is poorly understood. This systematic review aimed to explore whether s-IgA levels changed after psychosocial stress in subjects under the age of 18. Fifteen articles were included. s-IgA basal levels are increased in children older than 9 years old exposed to stress. Furthermore, s-IgA seems to follow a circadian rhythm, which is altered under stress conditions. Finally, the collective evidence suggests that salivary s-IgA rapidly increases under acute stress after puberty. Overall, our review indicates that s-IgA could be considered a potential psychosocial stress biomarker of interest for pediatric and child-juvenile psychiatric population. Further studies are needed to validate the role of s-IgA circadian rhythm and basal levels as psychosocial stress biomarkers and disentangle the role of age and type of stressor.

Developmental Cascades Link Maternal-Newborn Skin-to-Skin Contact with Young Adults' Psychological Symptoms, Oxytocin, and Immunity; Charting Mechanisms of Developmental Continuity from Birth to Adulthood

Premature birth disrupts the continuity of maternal-newborn bodily contact, which underpins the development of physiological and behavioral support systems. Utilizing a unique cohort of mother-preterm dyads who received skin-to-skin contact (Kangaroo Care, KC) versus controls, and following them to adulthood, we examined how a touch-based neonatal intervention impacts three adult outcomes; anxiety/depressive symptoms, oxytocin, and secretory immunoglobulin A (s-IgA), a biomarker of the immune system. Consistent with dynamic systems' theory, we found that links from KC to adult outcomes were indirect, mediated by its effects on maternal mood, child attention and executive functions, and mother-child synchrony across development. These improvements shaped adult outcomes via three mechanisms; (a) "sensitive periods", where the infancy improvement directly links with an outcome, for instance, infant attention linked with higher oxytocin and lower s-IgA; (b) "step-by-step continuity", where the infancy improvement triggers iterative changes across development, gradually shaping an outcome; for instance, mother-infant synchrony was stable across development and predicted lower anxiety/depressive symptoms; and (c) "inclusive mutual-influences", describing cross-time associations between maternal, child, and dyadic factors; for instance, from maternal mood to child executive functions and back. Findings highlight the long-term impact of a birth intervention across development and provide valuable insights on the mechanisms of "developmental continuity", among the key topics in developmental research.

Maternal Distress and Social Support Are Linked to Human Milk Immune Properties

Possible alterations of maternal immune function due to psychological stress may reflect immunoactive factor levels in breast milk. This study aimed to assess the association between maternal distress and breast milk levels of secretory IgA (SIgA), IgM, IgG, and lactoferrin (LF). We hypothesized that this association is moderated by maternal social support achieved from others during lactation. The study group included 103 lactating mothers and their healthy five-month-old infants. Maternal distress was determined based on the State Anxiety Inventory and the level of salivary cortisol. Social support was assessed using the Berlin Social Support Scales. Breast milk samples were collected to test for SIgA, IgM, IgG, and LF using the ELISA method. Milk immunoactive factors were regressed against maternal anxiety, social support, salivary cortisol, and infant gestational age using the general regression model. Maternal anxiety was negatively associated with milk levels of LF (β = -0.23, p = 0.028) and SIgA (β = -0.30, p = 0.004), while social support was positively associated with milk IgG (β = 0.25, p = 0.017). Neither anxiety nor social support were related to milk IgM. No association was found between the level of maternal salivary cortisol and immunoactive factors in milk. Our results suggest that maternal psychological wellbeing and social support may affect milk immune properties.

The association of physical fitness with mental health in children: A serial multiple mediation model

There is growing interest in the association between physical fitness and mental health. This study aimed to extend current knowledge by investigating the potential mediating roles of resilience and anxiety in the association between physical fitness and mental health in children. A total of 269 children were selected by stratified random sampling from three primary schools in China. Physical fitness was scored using the Chinese National Student Physical Fitness Standard. Resilience, anxiety, and mental health data were collected using the following questionnaires: Resilience Scale for Chinese Adolescents, Multidimensional Anxiety Scale for Children, and the Mental Health Test. The PROCESS macro developed by Hayes was used to conduct serial multiple mediation analysis. We found that physical fitness, resilience, anxiety, and mental health were significantly correlated. Children with higher physical fitness had lower mental health problems; however, this statistical significance was not detectable after controlling for resilience and anxiety. Serial multiple mediation analysis revealed that the association of physical fitness with mental health was partially mediated by resilience and anxiety. These results indicate that the positive association of physical fitness with mental health in children may be changed through resilience and anxiety, which appear to play serial multiple mediating roles in this association. These findings contribute to deeper understanding of the associations between these factors and suggest that promoting physical fitness independent of considering resilience and anxiety may be insufficient to achieve good mental health in children.

Young Children Display Diurnal Patterns of Salivary IgA and Alpha-Amylase Expression Which Are Independent of Food Intake and Demographic Factors

BACKGROUND

Salivary alpha-amylase (sAA) and salivary immunoglobulin A (sIgA) have been proposed as biomarkers for research on the mucosal immune system and on stress. Expression of both sAA and sIgA has been described to follow opposing diurnal patterns. This knowledge is crucial for the interpretation of studies using these biomarkers.

AIM

It was hypothesized that sAA and sIgA display diurnal patterns in children and that this is independent of food intake or demographic factors.

METHODS

Whole saliva was collected from 78 healthy children (15-39 months old) in the morning and evening for two random nonconsecutive days. The samples have been analysed for sAA and sIgA. The total daily energy, fat, saturated fat, protein, carbohydrate and fibre, mineral, and vitamin consumption were analysed based on the two-day weighed food records collected by the parents.

RESULTS

It was demonstrated that most young children followed the diurnal pattern when sAA increased and sIgA decreased from morning to evening. No correlation was observed between the intake of any of the nutrients and morning or evening values for both salivary proteins. The morning and evening values of sAA and sIgA did not correlate with age, sex, Asian ethnicity, and BMI of the children.

CONCLUSION

Diurnal patterns of sAA and sIgA exist in healthy young children and are not affected by their nutrient intake, sex, Asian ethnicity, and BMI. Scientists including sIgA and sAA in their research must consider the diurnal pattern that these markers exhibit and design the study accordingly.

Stress and immune biomarkers interact with parenting behavior to shape anxiety symptoms in trauma-exposed youth

The relations between stress, HPA-axis, and the immune system have been extensively studied; however, no study to date addressed the joint contribution of immune and HPA biomarkers to the development of anxiety in youth exposed to chronic trauma as mediated by mother-child interaction patterns. A unique cohort of war-exposed children and their mothers, compared to matched controls, were followed from infancy and the current study reports findings from early adolescence (mean age = 11.66, SD = 1.23; N = 111; exposed = 58 control = 53). Youth and mothers' salivary cortisol (CT) and secretory immunoglobulin (s-IgA) levels were measured three times during a 4-hour lab visit, mother-child interaction patterns were quantified from a joint task, and children's anxiety symptoms diagnosed. Trauma-exposed children had higher levels of CT and s-IgA, exhibited more anxiety symptoms, and showed lower social collaboration with mother during the joint task. Trauma-exposed mothers had higher CT and s-IgA levels and showed less supportive parenting during mother-child interaction. Structural equation modeling defined three bio-behavioral paths by which trauma increases anxiety in youth. While the first path charted a behavioral link from exposure to child anxiety via diminished maternal support, the other two paths described mediated biological paths, one through HPA-axis functioning, the other via the immune system. Paths via the child's HPA and immune system were mediated by the parallel maternal variable. Findings are the first to describe the complex bio-behavioral interplay of stress and immune biomarkers and parenting behavior in shaping to the development of risk and resilience trajectories in youth growing up amidst chronic trauma.