Mammary epithelium permeability during established lactation: associations with cytokine levels in human milk

Objective

The cytokine profile of human milk may be a key indicator of mammary gland health and has been linked to infant nutrition, growth, and immune system development. The current study examines the extent to which mammary epithelium permeability (MEP) is associated with cytokine profiles during established lactation within a sample of US mothers.

Methods

Participants were drawn from a previous study of human milk cytokines. The present analysis includes 162 participants (98 Black, 64 White) with infants ranging from 1 to 18 months of age. Levels of cytokines were determined previously. Here we measure milk sodium (Na) and potassium (K) levels with ion-selective probes. Two approaches were used to define elevated MEP: Na levels ≥10 mmol/L and Na/K ratios greater than 0.6. Associations between maternal-infant characteristics, elevated MEP, and twelve analytes (IL-6, IL-8, TNFα, IL-1β, FASL, VEGFD, FLT1, bFGF, PLGF, EGF, leptin, adiponectin) were examined using bivariate associations, principal components analysis, and multivariable logistic regression models.

Results

Elevated MEP was observed in 12 and 15% of milk samples as defined by Na and Na/K cutoffs, respectively. The odds of experiencing elevated MEP (defined by Na ≥ 10 mmol/L) were higher among Black participants and declined with older infant age. All cytokines, except leptin, were positively correlated with either Na or the Na/K ratio. A pro-inflammatory factor (IL-6, IL-8, TNFα, IL-1β, EGF) and a tissue remodeling factor (FASL, VEGFD, FLT1, bFGF, PLGF, adiponectin) each contributed uniquely to raising the odds of elevated MEP as defined by either Na or the Na/K ratio.

Conclusion

This exploratory analysis of MEP and cytokine levels during established lactation indicates that elevated MEP may be more common in US populations than previously appreciated and that individuals identifying as Black may have increased odds of experiencing elevated MEP based on current definitions. Research aimed at understanding the role of MEP in mammary gland health or infant growth and development should be prioritized.

Grounded in Community: Development of a Birth Justice-Focused Volunteer Birth Companion Program

Continuous labor support is an evidence-based practice demonstrated to improve birth outcomes, particularly when provided by a trained doula or birth companion. Access to doula services designed to meet the needs of historically underserved and diverse communities can mitigate the negative effects of structural racism and health disparities in perinatal care. Unfortunately, continuous labor support by a companion of choice is not universally supported. This leaves individuals with limited resources unable to access services from a trained doula. Volunteer birth companion programs are one model for increasing access to continuous labor support by bringing the community into the hospital. This article describes a birth justice-focused volunteer birth companion program that evolved out of a multistakeholder collaboration between community birth workers, local reproductive justice organizations, and hospital-based providers, staff, and administrators in direct response to community needs. This program is unique in its collaborative development, grounding in core values, and design of a reproductive justice-focused curriculum that includes training in diversity, inclusion, and care for clients with a history of trauma or perinatal substance use. Key takeaways include recommendations to center client needs, consider sustainability, and embrace flexibility and change. Discussion includes recognition of the strengths and limitations of a volunteer-based model, including acknowledgment that volunteer birth work, while filling an important gap, necessitates the privilege of having sufficient time, economic freedom, and social support. Ensuring universal insurance coverage for doula services has the potential to increase access to continuous labor support, improve birth outcomes, and diversify the birth workforce.

Perinatal Behavioral Health, the COVID-19 Pandemic, and a Social Determinants of Health Framework

The United States has greater prevalence of mental illness and substance use disorders than other developed countries, and pregnant women are disproportionately affected. The current global COVID-19 pandemic, through the exacerbation of psychological distress, unevenly affects the vulnerable population of pregnant women. Social distancing measures and widespread closures of businesses secondary to COVID-19 are likely to continue for the foreseeable future and to further magnify psychosocial risk factors. We propose the use of a social determinants of health framework to integrate behavioral health considerations into prenatal care and to guide the implementation of universal and comprehensive psychosocial assessment in pregnancy. As the most numerous and well-trusted health care professionals, nurses are ideally positioned to influence program and policy decisions at the community and regional levels and to advocate for the full integration of psychosocial screening and behavioral health into prenatal and postpartum care as core components.

Improved breastfeeding duration with Baby Friendly Hospital Initiative implementation in a diverse and underserved population

BACKGROUND

Few studies have evaluated the impact of Baby Friendly Hospital Initiative (BFHI) implementation on underserved populations in the United States. We undertook this study in New Mexico, a large southwestern state with a diverse population and limited health care access.

METHODS

A quasi-experimental, retrospective cohort design was used to compare short-term breastfeeding duration between a pre-BFHI and a post-BFHI cohort. Among the post-BFHI cohort, logistic regression models were fitted to predict short-term breastfeeding duration from both individual and cumulative exposure to inpatient maternity care practices (Steps 4 to 9).

RESULTS

Implementation of the BFHI and cumulative exposure to the Ten Steps increased short-term duration of any breastfeeding and exclusive breastfeeding at 2-6 weeks postpartum. Exposure to all six of the inpatient Ten Steps increased the odds of any breastfeeding by 34 times and exclusive breastfeeding by 24 times. Exposure to Step 9 ("Give no pacifiers or artificial nipples") uniquely increased the likelihood of any breastfeeding at 2-6 weeks postpartum by 5.7 times, whereas Step 6 ("Give infants no food or drink other than breastmilk") increased the rate of exclusive breastfeeding by 4.4 times at 2-6 weeks postpartum.

CONCLUSION

These findings demonstrate that the Baby Friendly Hospital Initiative can have a positive impact on breastfeeding among underserved populations.

The ups and downs of early mothering

INTRODUCTION

The maternal experience of having a young infant is often viewed through a negative lens focused on psychological distress due, in part, to a historical focus on identifying threats to prenatal, perinatal and postpartum well-being of women and infants. This report examines maternal appraisal of both positive and negative experiences during and after pregnancy and introduces a new scale that assesses both uplifts and hassles that are specific to early motherhood.

METHODS

The sample included 136 women who began study participation during pregnancy and completed an existing scale designed to evaluate pregnancy-specific hassles and uplifts. When infants were 6 months old, participants completed the newly developed Maternal Experience Scale (MES) along with questionnaires related to anxiety, depression, attachment, parenting stress and infant temperament characteristics.

RESULTS

In general, women with 6-month-old infants rated their maternal experiences far more positively than negatively. MES hassles and uplift scores reflected both convergent and discriminant validity with general measures of psychological well-being and parent-specific measures. Appraisal of the pregnancy experience significantly predicted appraisal of early motherhood for hassles, uplifts and a composite score reflecting emotional valence. Women became relatively more uplifted and less hassled from pregnancy to 6-month postpartum; this was particularly true for multiparous women.

DISCUSSION

The maternal perception of motherhood corresponds to her perception of pregnancy. The MES provides a balanced view of motherhood by including maternal appraisal of the uplifting aspects of caring for an infant.

Salivary cortisol mediates effects of poverty and parenting on executive functions in early childhood

In a predominantly low-income population-based longitudinal sample of 1,292 children followed from birth, higher level of salivary cortisol assessed at ages 7, 15, and 24 months was uniquely associated with lower executive function ability and to a lesser extent IQ at age 3 years. Measures of positive and negative aspects of parenting and household risk were also uniquely related to both executive functions and IQ. The effect of positive parenting on executive functions was partially mediated through cortisol. Typical or resting level of cortisol was increased in African American relative to White participants. In combination with positive and negative parenting and household risk, cortisol mediated effects of income-to-need, maternal education, and African American ethnicity on child cognitive ability.

Direct and moderating links of salivary alpha-amylase and cortisol stress-reactivity to youth behavioral and emotional adjustment

Recent studies have revealed evidence for interactions between autonomic nervous system (ANS) activity, indexed by saliva alpha amylase (sAA), and hypothalamic-pituitary-adrenocortical activity, in predicting psychological functioning. The present study extends this work by examining individual differences in sAA and cortisol stress reactivity in relation to behavioral and emotional adjustment in youth. Participants were 56 healthy children (age 7-16). sAA, cortisol, and other physiological and affective responses were measured before, during, and after stressor tasks (either performance or peer rejection). Basal and stress responsive sAA and cortisol as well as their interactions were assessed in relation to externalizing and internalizing behaviors and trait anxiety. sAA was positively related to anxiety, while sAA reactivity moderated associations between cortisol reactivity and problem behavior. Results highlight the importance of measuring multiple physiological systems to elucidate mechanisms underlying behavioral and emotional dysregulation.

Maternal salivary cortisol differs by fetal sex during the second half of pregnancy

Maternal salivary cortisol was measured at weekly intervals from 24 to 38 weeks gestation. The total sample consisted of 120 women enrolled in staggered intervals in such a way as to generate weekly measures of salivary cortisol during the latter half of pregnancy. Hierarchical linear modeling revealed the expected increase in unbound maternal cortisol during this period, with a slight deceleration in rate of increase at 33 weeks gestation. Women carrying male fetuses had higher levels of salivary cortisol initially as compared to women carrying female fetuses; at 30 weeks gestation there was cross-over such that higher maternal cortisol was observed in women carrying female fetuses beyond this time and through term. Results highlight the importance of considering fetal sex as a moderator of contemporaneous and predictive associations between maternal cortisol and prenatal or postnatal development.

Prenatal antecedents of newborn neurological maturation

Fetal neurobehavioral development was modeled longitudinally using data collected at weekly intervals from 24 to 38 weeks gestation in a sample of 112 healthy pregnancies. Predictive associations between 3 measures of fetal neurobehavioral functioning and their developmental trajectories to neurological maturation in the first weeks after birth were examined. Prenatal measures included fetal heart rate (FHR) variability, fetal movement, and coupling between fetal motor activity and heart rate patterning; neonatal outcomes include a standard neurologic examination (n = 97) and brainstem auditory evoked potential (BAEP; n = 47). Optimality in newborn motor activity and reflexes was predicted by fetal motor activity, FHR variability, and somatic-cardiac coupling predicted BAEP parameters. Maternal pregnancy-specific psychological stress was associated with accelerated neurologic maturation.

Fetal motor activity and maternal cortisol

The contemporaneous association between maternal salivary cortisol and fetal motor activity was examined at 32 and 36 weeks gestation. Higher maternal cortisol was positively associated with the amplitude of fetal motor activity at 32 weeks, r(48) = .39, p < .01, and 36 weeks, r(77) = .27, p < .05, and the amount of time fetuses spent moving at 32 weeks during the 50 min observation period, r(48) = 33, p < .05. Observation of periods of unusually intense fetal motor activity were more common in fetuses of women with higher cortisol, Mann-Whitney U = 58.5. There were no sex differences in fetal motor activity, but the associations between maternal cortisol and fetal motor amplitude and overall movement were significantly stronger for male than female fetuses.

Maternal methadone dosing schedule and fetal neurobehaviour

OBJECTIVE

Daily methadone maintenance is the standard of care for opiate dependency during pregnancy. Previous research has indicated that single-dose maternal methadone administration significantly suppresses fetal neurobehaviours. The purpose of this study was to determine if split-dosing would have less impact on fetal neurobehaviour than single-dose administration.

METHODS

Forty methadone-maintained women were evaluated at peak and trough maternal methadone levels on single- and split-dosing schedules. Monitoring sessions occurred at 36- and 37-weeks gestation in a counterbalanced study design. Fetal measures included heart rate, variability, accelerations, motor activity and fetal movement-heart rate coupling (FM-FHR). Maternal measures included heart period, variability, skin conductance, respiration and vagal tone. Repeated measure analysis of variance was used to evaluate within-subject changes between split- and single-dosing regimens.

RESULTS

All fetal neurobehavioural parameters were suppressed by maternal methadone administration, regardless of dosing regimen. Fetal parameters at peak were significantly lower during single versus split methadone administration. FM-FHR coupling was less suppressed from trough to peak during split-dosing versus single-dosing. Maternal physiologic parameters were generally unaffected by dosing condition.

CONCLUSION

Split-dosed fetuses displayed less neurobehavioural suppression from trough to peak maternal methadone levels as compared with single-dosed fetuses. Split-dosing may be beneficial for methadone-maintained pregnant women.

Stress response and the adolescent transition: performance versus peer rejection stressors

Little is known about normative variation in stress response over the adolescent transition. This study examined neuroendocrine and cardiovascular responses to performance and peer rejection stressors over the adolescent transition in a normative sample. Participants were 82 healthy children (ages 7-12 years, n = 39, 22 females) and adolescents (ages 13-17, n = 43, 20 females) recruited through community postings. Following a habituation session, participants completed a performance (public speaking, mental arithmetic, mirror tracing) or peer rejection (exclusion challenges) stress session. Salivary cortisol, salivary alpha amylase (sAA), systolic and diastolic blood pressure (SBP, DBP), and heart rate were measured throughout. Adolescents showed significantly greater cortisol, sAA, SBP, and DBP stress response relative to children. Developmental differences were most pronounced in the performance stress session for cortisol and DBP and in the peer rejection session for sAA and SBP. Heightened physiological stress responses in typical adolescents may facilitate adaptation to new challenges of adolescence and adulthood. In high-risk adolescents, this normative shift may tip the balance toward stress response dysregulation associated with depression and other psychopathology. Specificity of physiological response by stressor type highlights the importance of a multisystem approach to the psychobiology of stress and may also have implications for understanding trajectories to psychopathology.

Diurnal rhythm of cortisol during late pregnancy: associations with maternal psychological well-being and fetal growth

Maternal psychological functioning during pregnancy affects both maternal and fetal well-being. The hypothalamic-pituitary-adrenal (HPA) axis provides one mechanism through which maternal psychosocial factors may be transduced to the fetus. However, few studies have examined maternal psychological factors or birth outcomes in relation to the diurnal pattern of cortisol across the day. The current study examined maternal psychological well-being, parity status, and birth weight in relation to the maternal cortisol diurnal rhythm in a group of 98 low-risk pregnant women (51 primiparae). At 36 weeks gestation, participants completed both pregnancy-specific and general self-report measures of psychological functioning and provided saliva samples at 8:00, 12:00, and 16:00 h on 2 consecutive working days for the assay of cortisol. The expected diurnal decline in salivary cortisol was observed. Higher trait anxiety was associated with a flatter afternoon decline for all mothers. For primiparae, steeper morning cortisol declines were associated with lower infant birth weight. The findings suggest that regulation of the HPA axis may differ by parity status with downstream implications for fetal growth and development.

Integration of salivary biomarkers into developmental and behaviorally-oriented research: problems and solutions for collecting specimens

Saliva has been championed as a diagnostic fluid of the future. Much of the attention that saliva receives as a biological specimen is due to the perception that the nature of sample collection is quick, uncomplicated, and non-invasive. In most cases, this perception matches reality; however, in some special circumstances and populations collecting saliva can be unexpectedly difficult, time consuming, and may not yield sufficient sample volume for assay. In this report, we review the nature and circumstances surrounding some of these problems in the context of developmental science and then present alternatives that can be used by investigators to improve the next generation of studies. We expect our findings will ease the burden on research participants and assistants, reduce the rate of missing values in salivary data sets, and increase the probability that salivary biomarkers will continue to be successfully integrated into developmental and behaviorally-oriented research.

Salivary -Amylase in Biobehavioral Research: Recent Developments and Applications

In the history of science, technical advances often precede periods of rapid accumulation of knowledge. Within the past three decades, discoveries that enabled the noninvasive measurement of the psychobiology of stress (in saliva) have added new dimensions to the study of health and human development. This widespread enthusiasm has led to somewhat of a renaissance in behavioral science. At the cutting edge, the focus is on testing innovative theoretical models of individual differences in behavior as a function of multilevel biosocial processes in the context of everyday life. Several new studies have generated renewed interest in salivary alpha-amylase (sAA) as a surrogate marker of the autonomic/sympathetic nervous system component of the psychobiology of stress. This article reviews sAA's properties and functions; presents illustrative findings relating sAA to stress and the physiology of stress, behavior, cognitive function, and health; and provides practical information regarding specimen collection and assay. The overarching intent is to accelerate the learning curve such that investigators avoid potential pitfalls associated with integrating this unique salivary analyte into the next generation of biobehavioral research.

Individual differences in salivary cortisol: associations with common over-the-counter and prescription medication status in infants and their mothers

The purpose of the present study was to describe associations between the use of common over-the-counter (OTC) and prescription medications with individual differences in salivary cortisol in infants and their mothers. Participants were 1020 mothers and 852 infants (52.5% boys; ages 5.03-13.44 months) from economically disadvantaged and ethnically diverse families (38.4% African American) who donated saliva samples before, 20 and 40 min after infants participated in a series of challenging tasks. Samples (N=5616) were later assayed for cortisol. Medication information was content analyzed separately for infants (e.g., teething gels, nonsteroidal anti-inflammatory drugs, acetaminophen, decongestants) and mothers (e.g., narcotics, antidepressants, antipsychotics, contraceptives, glucocorticoids). A large percentage of infants (44%) and the majority of mothers (57.5%) had used at least one medication (range 0-4) in the previous 48 h. Most frequent were acetaminophen (e.g., Tylenol) and cold medications (e.g., decongestants) for infants and contraceptives and acetaminophen for mothers. Compared to infants not taking any medications, cortisol reactivity to the challenge tasks was less pronounced for infants taking acetaminophen. Cortisol levels were higher for mothers taking oral or transdermal contraceptives and acetylsalicylic acid (e.g., Aspirin) but lower for mothers taking pure agonist opioids (e.g., Oxycontin) compared to mothers not taking any medications. These medication-related differences remained significant after controlling for sampling time, fever, maternal anxiety and depression, infant temperament, ethnicity, SES, and health status. Recommendations are provided to steer investigators clear of these potential sources of unsystematic error variance in salivary cortisol.

Salivary alpha-amylase response to competition: relation to gender, previous experience, and attitudes

This study examined individual differences in salivary alpha-amylase response to competition in relation to gender, previous experience, behavior, attitudes, and performance. Participants were 42 (21 women) members of a collegiate crew team. Saliva samples were collected before, 20- and 40-min post-ergometer competition and at the same times on a non-competition day for comparison. Samples were assayed for salivary biomarkers of sympathetic nervous system (alpha-amylase) and hypothalamic-pituitary-adrenal axis (cortisol) activity. Behavioral assessments included self-reports of dominance, competitiveness, bonding with teammates, competition-related strategic thinking, and performance. On average, salivary alpha-amylase increased 156% in response to the ergometer competition. By comparison, cortisol increased 87% across the same time period. Salivary alpha-amylase was higher across the competition for varsity than for novice athletes, and was positively associated with performance and interest in team-bonding. Regression analyses revealed that alpha-amylase reactivity explained individual differences in dominance and team bonding above and beyond that associated with cortisol reactivity, and that joint inactivation in alpha-amylase and cortisol reactivity to competition (low-low) was associated with high perceived dominance. The findings are among the first to integrate salivary alpha-amylase into the study of competition and reveal that intra-individual change in alpha-amylase may be influenced by a confluence of factors that include contextual, behavioral, and psychological factors and processes.

Bacteria in the oral mucosa and its effects on the measurement of cortisol, dehydroepiandrosterone, and testosterone in saliva

Bacteria load in saliva was experimentally manipulated, and the consequences for the measurement of salivary testosterone (T), dehydroepiandrosterone (DHEA), and cortisol (C) were examined. Healthy adults (n = 19) donated the first saliva sample upon rising after which they rinsed their mouths with water, waited 10 min, and donated a second sample. Samples were either left untreated or passed through a 0.22-microm filter and then frozen at -80 degrees C or incubated at room temperature (RT) for 10 days. Aliquots of each sample were cultured on agar to determine baseline and post-incubation (or freezing) bacteria load. Bacteria counts were not significantly influenced by rinsing (with water), were substantially reduced by filtration, and increased by incubation at RT. Average levels of salivary T and C, but not DHEA, were significantly lower in samples stored at RT than samples frozen the day of collection. The change in bacteria count induced by storing samples at RT was associated with a change in testosterone but not cortisol or DHEA. When samples were passed through a 0.22-microm filter bacteria counts were reduced, and the association between bacteria and testosterone was reduced to non-significant. These findings contribute to a growing body of literature revealing that the process of sample collection, storage, and handling can dramatically influence the accuracy of information generated when salivary biomarkers are integrated into research and clinical diagnostics.

Oxytocin is not a valid biomarker when measured in saliva by immunoassay

The integration of oxytocin (OT) into behavioral science seems to hold considerable promise for advancing our understanding of human health and development but methodological issues restrict the measurement of OT in large studies, in everyday social settings, or when repeated sampling is required. Measuring OT in saliva could overcome many of these limitations. In this paper, we rigorously evaluate the feasibility of doing so. A series of experiments leads to the conclusion that saliva does not contain oxytocin in measurable amounts, and that OT is not a valid salivary biomarker when measured by currently available immunological methods. Levels of immuno-reactive OT in saliva are primarily due to non-specific interference with antibody-antigen binding. We can state with a high degree of certainty that measurement of OT in saliva does not yield meaningful indices of individual differences or intra-individual change.

Blood contamination and the measurement of salivary progesterone and estradiol

The impact of blood leakage due to microinjury to the oral cavity on the measurement of salivary reproductive hormones was examined. Saliva samples were collected before, immediately after, and then every 15 min for 1 h following vigorous tooth brushing. Blood in saliva was quantified by visual inspection of discoloration and an immunoassay for transferrin. Levels of progesterone increased, and levels of estradiol decreased, in saliva after microinjury. These changes were present only immediately after microinjury. The findings have implications for the use of salivary assays in biobehavioral research, short-term dynamic investigations, pharmacokinetic analyses, and studies of chronobiological changes in progesterone and estradiol levels.

Gender differences in testosterone and cortisol response to competition

This study examined intra-individual change in testosterone, cortisol, and hormone-behavior relationships in response to a rowing ergometer competition. Forty-six members (23 females) of a university crew team provided saliva samples before, 20- and 40-min post-competition, as well as baselines on a non-competition day. Behavioral assessments included measures of previous rowing experience, dominance, competitiveness, bonding with teammates, pre- and post-competition mental state and performance. Men's and women's endocrine responses to this competitive setting were more different than alike and varied by level of competitive experience, the specific phase of the competitive event, and the particular hormone measured. Inter-individual differences in testosterone and cortisol were differentially associated with social affiliation with teammates but rarely with dominance or competitiveness. Theoretically, the findings support the integration of features of the 'tend and befriend' model with the biosocial model of status, and suggest future research directions that may lead to clarification and refinement of those ideas.

The "trouble" with salivary testosterone

In a series of studies, we identify several specific issues that can limit the value of integrating salivary testosterone in biosocial research. Salivary testosterone measurements can be substantially influenced during the process of sample collection, are susceptible to interference effects caused by the leakage of blood (plasma) into saliva, and are sensitive to storage conditions when samples have been archived. There are gender differences in salivary testosterone levels and variance, the serum-saliva association, the relationship of salivary testosterone to age and pubertal development, and the stability of individual differences in salivary testosterone levels over time. The findings have important implications at several levels of analysis for research that aims to test biosocial models of testosterone--behavior relationships. Recommendations are provided to steer investigators around these "troubles" with salivary testosterone.

Quantifying blood leakage into the oral mucosa and its effects on the measurement of cortisol, dehydroepiandrosterone, and testosterone in saliva

The impact of blood leakage due to microinjury to the oral cavity on the measurement of salivary hormones was examined. Saliva samples were collected before, immediately after, and then every 15 min for 1 h following vigorous tooth brushing. Blood in saliva was quantified by visual inspection of discoloration, Hemastix reagent strips to detect hemoglobin, and an immunoassay for transferrin. The presence of blood in saliva immediately after microinjury was confirmed by all methods. Hemoglobin and transferrin levels remained elevated over baseline for at least 30 min. Levels of salivary testosterone increased over baseline and remained elevated for 30 min in response to microinjury. Microinjury induced change in salivary testosterone was more closely associated with the change in transferrin than hemoglobin levels or discoloration ratings. On average, levels of salivary dehydroepiandrosterone (DHEA) did not increase in response to microinjury. However, individual differences in microinjury induced change in DHEA were associated with discoloration ratings. Salivary cortisol levels, on average, were neither responsive to microinjury, nor were individual differences in cortisol change associated with blood contamination measures. Neither diurnal nor gender-related differences in baseline hormone levels predicted the impact of blood leakage on quantitative salivary measurements. The findings suggest ecologically valid minor-to-moderate level microinjuries to the oral cavity have negligible effects on the measurement of salivary cortisol, but may be important to quantify and control when assessing other hormones especially testosterone.

Integrating biological, behavioral, and social levels of analysis in early child development: progress, problems, and prospects

Integration of noninvasive, biological measures into behavioral research has increased, but the interpretation of biobehavioral findings in relation to developmental outcomes is rarely straightforward. This commentary highlights the need for specific, theoretically derived hypotheses, multiple measures of behavioral and biological processes, and analytical strategies aimed at explaining interindividual differences in intraindividual change. It is suggested here that the next phase of biosocial research needs to move beyond description and toward development of mid-level theories that will enable researchers to specify, test, and refine hypotheses of how biobehavioral processes interact with social-contextual factors to influence development. These mid-level biosocial models will be necessary to determine whether individual differences in children's adrenocortical activity confer risk or resilience because of early or cumulative exposure to nonparental care.