First-time fathers show longitudinal gray matter cortical volume reductions: evidence from two international samples

Leveraging research into sex differences and steroid hormones to improve brain health

Sex differences, driven in part by steroid hormones, shape the structure and function of the brain throughout the lifespan and manifest across brain health and disease. The influence of steroid hormones on neuroplasticity, particularly in the adult hippocampus, differs between the sexes, which has important implications for disorders and diseases that compromise hippocampus integrity, such as depression and Alzheimer disease. This Review outlines the intricate relationship between steroid hormones and hippocampal neuroplasticity across the adult lifespan and explores how the unique physiology of male and female individuals can affect health and disease. Despite calls to include sex and gender in research, only 5% of neuroscience studies published in 2019 directly investigated the influence of sex. Drawing on insights from depression, Alzheimer disease and relevant hippocampal plasticity, this Review underscores the importance of considering sex and steroid hormones to achieve a comprehensive understanding of disease susceptibility and mechanisms. Such consideration will enable the discovery of personalized treatments, ultimately leading to improved health outcomes for all.

Protective role of parenthood on age-related brain function in mid- to late-life

The experience of human parenthood is near ubiquitous and can profoundly alter one's body, mind, and environment. However, we know very little about the long-term neural effects of parenthood for parents themselves, or the implications of pregnancy and caregiving experience on the aging adult brain. Here, we investigate the link between the number of children parented and age on brain function in 19,964 females and 17,607 males from the UK Biobank. In both females and males, parenthood was positively correlated with functional connectivity, such that higher number of children parented was associated with higher connectivity, particularly within the somato/motor network. Critically, the spatial topography of parenthood-linked effects was inversely correlated with the impact of age on functional connectivity across the brain for both females and males, such that the connections that were positively correlated with number of children were negatively correlated with age. This result suggests that a higher number of children is associated with patterns of brain function in the opposite direction to age-related alterations. Overall, these results indicate that the changes accompanying parenthood may confer benefits to brain health across the lifespan, altering aging trajectories, consistent with animal models of parenthood and preliminary findings of "younger-looking" brain structure in human parents. Observing this effect in both females and males implicates the caregiving environment, rather than pregnancy alone, and highlights the importance of future work to disentangle the underlying mechanisms related to the direct impact of caregiving, the indirect impact of the environment, and the result of covarying sociodemographic factors.

Pregnancy entails a U-shaped trajectory in human brain structure linked to hormones and maternal attachment

Growing evidence places the gestational period as a unique moment of heightened neuroplasticity in adult life. In this longitudinal study spanning pre, during, and post pregnancy, we unveil a U-shaped trajectory in gray matter (GM) volume, which dips in late pregnancy and partially recovers during postpartum. These changes are most prominent in brain regions associated with the Default Mode and Frontoparietal Network. The U-shaped trajectory is predominantly linked to gestational factors, as it only presents in gestational mothers and correlates with fluctuations in estrogens over time. Finally, the mother's mental health status mediates the relationship between postpartum GM volume recovery and maternal attachment at 6 months postpartum. This research sheds light on the complex interplay between hormones, brain development, and behavior during the transition to motherhood. It addresses a significant knowledge gap in the neuroscience of human pregnancy and opens new possibilities for interventions aimed at enhancing maternal health and well-being.

The parental brain, perinatal mental illness, and treatment: A review of key structural and functional changes

The transition to parenthood is perhaps the only time in adult life when the brain changes to such a significant degree in such a short period, particularly in birthing parents. It is also a time when there is an increased risk of developing a mental illness, which may be due, in part, to the increased neuroplasticity. Thus, we must develop interventions and treatments that support parents and promote parental brain health. This review will highlight key findings from current research on how human brain structure and function are modified with 1) the transition to parenthood, 2) parenting stress and perinatal mental illness, and 3) treatments aimed at promoting perinatal mental health. The focus will be on birthing parents and mothers, but brain changes in non-birthing parents will also be discussed. Improvements in our understanding of the parental brain, in health and with illness, will promote the well-being of generations to come.

Enduring maternal brain changes and their role in mediating motherhood's impact on well-being

Parenthood, particularly motherhood, is known to impact the structure and function of the brain in the short term, but the long-term effects of parenthood and their impacts on well-being are still poorly understood. This study explores the potential longer-term associations between parenthood and the brain, parenthood and well-being, and the potential role of brain modifications in influencing mothers' well-being. Using data from the UK Biobank, which includes brain imaging information from individuals aged 45-82 at the MRI scanning, we discovered differences in brain structure between mothers and non-mothers, with mothers exhibiting widely distributed higher gray matter density, particularly strong in frontal and occipital regions. No brain changes were observed in fathers. Parents reported a higher sense of life's meaning compared to their childless counterparts. Gray matter changes did not mediate the relationship between motherhood and well-being. This suggests that the alterations in gray matter associated with motherhood do not play a deterministic role in shaping long-term changes in well-being.

Parental status and markers of brain and cellular age: A 3D convolutional network and classification study

Recent research shows prominent effects of pregnancy and the parenthood transition on structural brain characteristics in humans. Here, we present a comprehensive study of how parental status and number of children born/fathered links to markers of brain and cellular ageing in 36,323 UK Biobank participants (age range 44.57-82.06 years; 52% female). To assess global effects of parenting on the brain, we trained a 3D convolutional neural network on T1-weighted magnetic resonance images, and estimated brain age in a held-out test set. To investigate regional specificity, we extracted cortical and subcortical volumes using FreeSurfer, and ran hierarchical clustering to group regional volumes based on covariance. Leukocyte telomere length (LTL) derived from DNA was used as a marker of cellular ageing. We employed linear regression models to assess relationships between number of children, brain age, regional brain volumes, and LTL, and included interaction terms to probe sex differences in associations. Lastly, we used the brain measures and LTL as features in binary classification models, to determine if markers of brain and cellular ageing could predict parental status. The results showed associations between a greater number of children born/fathered and younger brain age in both females and males, with stronger effects observed in females. Volume-based analyses showed maternal effects in striatal and limbic regions, which were not evident in fathers. We found no evidence for associations between number of children and LTL. Classification of parental status showed an Area under the ROC Curve (AUC) of 0.57 for the brain age model, while the models using regional brain volumes and LTL as predictors showed AUCs of 0.52. Our findings align with previous population-based studies of middle- and older-aged parents, revealing subtle but significant associations between parental experience and neuroimaging-based surrogate markers of brain health. The findings further corroborate results from longitudinal cohort studies following parents across pregnancy and postpartum, potentially indicating that the parenthood transition is associated with long-term influences on brain health.

Protective role of parenthood on age-related brain function in mid- to late-life

The experience of parenthood can profoundly alter one's body, mind, and environment, yet we know little about the long-term associations between parenthood and brain function and aging in adulthood. Here, we investigate the link between number of children parented (parity) and age on brain function in 19,964 females and 17,607 males from the UK Biobank. In both females and males, increased parity was positively associated with functional connectivity, particularly within the somato/motor network. Critically, the spatial topography of parity-linked effects was inversely correlated with the impact of age on functional connectivity across the brain for both females and males, suggesting that a higher number of children is associated with patterns of brain function in the opposite direction to age-related alterations. These results indicate that the changes accompanying parenthood may confer benefits to brain health across the lifespan, highlighting the importance of future work to understand the associated mechanisms.

Cortical volume reductions in men transitioning to first-time fatherhood reflect both parenting engagement and mental health risk

Perinatal reductions in gray matter volume have been observed in human mothers transitioning to parenthood, with preliminary evidence for similar changes in fathers. These reductions have been theorized to support adaptation to parenting, but greater investigation is needed. We scanned 38 first-time fathers during their partner's pregnancy and again after 6 months postpartum, and collected self-report data prenatally and 3, 6, and 12 months postpartum. Significant gray matter volume reductions were observed across the entire cortex but not the subcortex. Fathers who reported stronger prenatal bonding with the unborn infant, and planned to take more time off from work after birth, subsequently showed larger cortical volume decreases. Larger reductions in gray matter volume also emerged among fathers who reported stronger postpartum bonding with the infant, lower parenting stress, and more time spent with their infant. Larger volume reductions predicted more postpartum sleep problems and higher levels of postpartum depression, anxiety, and psychological distress, controlling for prenatal sleep and mental health. Volume reductions were smaller among fathers whose infants were older at the postpartum scan, indicating potential rebound. These results suggest that perinatal gray matter volume reductions might reflect not only greater parenting engagement but also increased mental health risk in new fathers.

Recalibration of the stress response system over adult development: Is there a perinatal recalibration period?

During early life-sensitive periods (i.e., fetal, infancy), the developing stress response system adaptively calibrates to match environmental conditions, whether harsh or supportive. Recent evidence suggests that puberty is another window when the stress system is open to recalibration if environmental conditions have shifted significantly. Whether additional periods of recalibration exist in adulthood remains to be established. The present paper draws parallels between childhood (re)calibration periods and the perinatal period to hypothesize that this phase may be an additional window of stress recalibration in adult life. Specifically, the perinatal period (defined here to include pregnancy, lactation, and early parenthood) is also a developmental switch point characterized by heightened neural plasticity and marked changes in stress system function. After discussing these similarities, lines of empirical evidence needed to substantiate the perinatal stress recalibration hypothesis are proposed, and existing research support is reviewed. Complexities and challenges related to delineating the boundaries of perinatal stress recalibration and empirically testing this hypothesis are discussed, as well as possibilities for future multidisciplinary research. In the theme of this special issue, perinatal stress recalibration may be a mechanism of multilevel, multisystem risk, and resilience, both intra-individually and intergenerationally, with implications for optimizing interventions.

Why and How to Account for Sex and Gender in Brain and Behavioral Research

Long overlooked in neuroscience research, sex and gender are increasingly included as key variables potentially impacting all levels of neurobehavioral analysis. Still, many neuroscientists do not understand the difference between the terms "sex" and "gender," the complexity and nuance of each, or how to best include them as variables in research designs. This TechSights article outlines rationales for considering the influence of sex and gender across taxa, and provides technical guidance for strengthening the rigor and reproducibility of such analyses. This guidance includes the use of appropriate statistical methods for comparing groups as well as controls for key covariates of sex (e.g., total intracranial volume) and gender (e.g., income, caregiver stress, bias). We also recommend approaches for interpreting and communicating sex- and gender-related findings about the brain, which have often been misconstrued by neuroscientists and the lay public alike.

Theory of mind during pregnancy and postpartum: A systematic review

Pregnancy is associated with prominent structural changes in brain areas involved in Theory of Mind (ToM), pointing to the possibility of modifications in ToM-related behavior and brain responses in parents. We performed a systematic review screening for studies that examined ToM in pregnant and/or early postpartum parents. The evaluation of the included 12 studies allowed us to construct an overview of ToM changes during pregnancy and postpartum as well as other associated factors, such as oxytocin, mental health, and parental behavior. Four studies examined ToM changes by comparing pregnant/early postpartum parents with nulliparous parents or prepregnancy measures. They reported no differences between groups measured with a self-report questionnaire but found group differences using an experimental approach. The results from the summarized studies further suggest a mediatory role of oxytocin between ToM and certain parental behavior. In addition, while no link between postpartum depression and ToM was observed, findings do point to an association between depressive and remote maternal behavior and anxious attachment style and ToM abilities in pregnant participants. Research findings regarding the interaction of ToM with both parity and maternal attachment to the fetus are ambivalent. Overall, research on this topic is scarce, limiting our ability to draw firm conclusions and stressing the need for further research on this topic. This review presents an overview of research findings on ToM and associated factors in pregnancy and the postpartum period and discusses directions for future research.

Parental experience is linked with lower vasopressin receptor 1a binding and decreased postpartum androgens in titi monkeys

Parenting induces many neurological and behavioral changes that enable parents to rear offspring. Vasopressin plays an important role in this process via its effects on cognition, affect, and neuroplasticity, and in some cases, via interactions with decreased parental androgens. Thus far, the role of these hormones has been primarily studied in rodents. To address this gap, we explored vasopressin receptors and androgens in titi monkeys, a pair-bonding and biparental primate species. In Studies 1 and 2, we used receptor autoradiography to correlate arginine vasopressin receptor 1a (AVPR1a) binding in the hippocampus (Study 1, n = 10) and the rest of the forebrain (Study 2, n = 23) with parental status, parental experience, parity, infant carrying, and pair affiliation. We found that parents exhibited lower AVPR1a binding than non-parents throughout most brain regions assessed, with especially strong effects in the hippocampus (β = -.61), superior colliculus (β = -.88), lateral septum (β = -.35), and medial preoptic area (β = -.29). The other measures of parental experience also tended to be negatively associated with AVPR1a binding across different brain regions. In Study 3 (n = 44), we compared pre- and postpartum urinary androgen levels in parents and non-parents and found that mothers exhibited a sustained androgen decrease across 3-4 months postpartum (relative to 3 months prepartum; β ranged from -.72 to -.62 for different comparisons). For males, we found that multiparous fathers exhibited decreased androgen levels at 1-2 weeks postpartum (β = -.25) and at 3-4 months postpartum (β = -.40) compared to the prepartum, indicating both immediate and long-term reductions with subsequent paternal experience. Together, the results of this study suggest that decreases in AVPR1a binding and circulating androgens are associated with parental behavior and physiology in titi monkeys.

Chronic Diseases in Children as a Challenge for Parenting

To be a parent or a caregiver in a modern society is a very difficult task, including multiple demands and expectations. Parenting imposes a special role in the life of any couple, especially for the mother, roles which must be learned through personal education, enriched by transgenerational experience. Chronic disease is recognized as a large stressor that affects the current situation of a child and a child's family. In this difficult situation, the family must go through a process of learning how to cope with it. In the family, where a child has a long-term health problem, there are certain behaviours that hinder the normal functioning of family relationships. According to the experience of many researchers, including my own, there is an indication that a child's illness often leads to the divorce of the parents. The fathers of sick children are often the initiators of such decisions. The purpose of this article was to find if there are differences in parenting between mothers and fathers of chronically ill children. The methodology is comprised of a review of published articles in PubMed over the last two decades related to parenting when there is chronic illness in children. More than 500 articles related to the topic were found. Obtained results were discussed.

Matrescence: lifetime impact of motherhood on cognition and the brain

Profound environmental, hormonal, and neurobiological changes mark the transition to motherhood as a major biosocial life event. Despite the ubiquity of motherhood, the enduring impact of caregiving on cognition and the brain across the lifespan is not well characterized and represents a unique window of opportunity to investigate human neural and cognitive development. By integrating insights from the human and animal maternal brain literatures with theories of cognitive ageing, we outline a framework for understanding maternal neural and cognitive changes across the lifespan. We suggest that the increased cognitive load of motherhood provides an initial challenge during the peripartum period, requiring continuous adaptation; yet when these demands are sustained across the lifespan, they result in increased late-life cognitive reserve.