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This paper examines causal sibling spillover effects among students from different family backgrounds in elementary and middle school. Family backgrounds are captured by race, household structure, mothers' educational attainment, and school poverty. Exploiting discontinuities in school starting age created by North Carolina school-entry laws, we adopt a quasi-experimental approach and compare test scores of public school students whose older siblings were born shortly before and after the school-entry cutoff date. We find that individuals whose older siblings were born shortly after the school-entry cutoff date have significantly higher test scores in middle school, and that this positive spillover effect is particularly strong in disadvantaged families. We estimate that the spillover effect accounts for approximately one third of observed statistical associations in test scores between siblings, and the magnitude is much larger for disadvantaged families. Our results suggest that spillover effects from older to younger siblings may lead to greater divergence in academic outcomes and economic inequality between families.

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Almost all research on son preference and the consequent sex differentials in child health has focused on India. Pakistan-a country with the second strongest stated desire for sons, no evidence of sex-selective abortion, and relatively high fertility-offers a different context in which to understand unequal health outcomes for boys and girls. I use three rounds of the Pakistan Demographic and Health Survey to examine sex differentials in child healthcare receipt across different family contexts. I find evidence of generalized discrimination: all girls, regardless of sibling composition or birth order, are less likely to receive full immunization or medical treatment. I do not find evidence that girls with older sisters face greater discrimination than other girls. For boys, I find some evidence of selective preferential treatment: among larger families, first sons are more likely to receive healthcare than other sons or daughters.

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Background: Comorbidity between psychopathologies may be attributed to genetic and environmental differences between people as well as causal processes within individuals, where one pathology increases risk for another. Disentangling between-person (co)variance from within-person processes of psychopathology dimensions across childhood may shed light on developmental causes of comorbid mental health problems. Here, we aim to determine whether and to what extent directional relationships between psychopathology dimensions within-person, and between individuals within families, play a role in comorbidity. Methods: We conducted random intercepts cross-lagged panel model (RI-CLPM) analyses to unravel the longitudinal co-occurrence of child psychopathology dimensions, jointly estimating between-person and within-person processes from childhood to early adolescence (age 7-12). We further developed an extension of the model to estimate sibling effects within-family (wf-RI-CLPM). Analyses were separately conducted in two large population-based cohorts, TEDS and NTR, including parent-rated measures of child problem behaviours based on the SDQ and CBCL scales respectively. Results: We found evidence for strong between-person effects underlying the positive intercorrelation between problem behaviours across time. Beyond these time-varying within-person processes accounted for an increasing amount of trait variance, within- and cross-trait, overtime in both cohorts. Lastly, by accommodating family level data, we found evidence for reciprocal directional influences within sib-pairs longitudinally. Conclusions: Our results indicate that within-person processes partly explain the co-occurrence of psychopathology dimensions across childhood, and within sib-pairs. Analyses provided substantive results on developmental processes underlying comorbidity in behavioural problems. Future studies should consider different developmental timeframes to shed more light on the processes contributing to developmental comorbidity.

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Many mammals grow up with siblings, and interactions between them can influence offspring phenotype and fitness. Among these interactions, sibling competition between different-age offspring should lead to reproductive and survival costs on the younger sibling, while sibling cooperation should improve younger sibling's reproductive potential and survival. However, little is known about the consequences of sibling effects on younger offspring life-history trajectory, especially in long-lived mammals. We take advantage of a large, multigenerational demographic dataset from semi-captive Asian elephants to investigate how the presence and sex of elder siblings influence the sex, survival until 5 years old, body condition, reproductive success (i.e. age at first reproduction and lifetime reproductive success) and long-term survival of subsequent offspring. We find that elder siblings have heterogeneous effects on subsequent offspring life-history traits depending on their presence, their sex and the sex of the subsequent offspring (named focal calf). Overall, the presence of an elder sibling (either sex) strongly increased focal calf long-term survival (either sex) compared to sibling absence. However, elder sisters had higher impact on the focal sibling than elder brothers. Focal females born after a female display higher long-term survival, and decreased age at first reproduction when raised together with an elder sister rather than a brother. Focal males born after a female rather than a male showed lower survival but higher body weight when both were raised together. We did not detect any sibling effects on the sex of the focal calf sex, survival until 5 years old and lifetime reproductive success. Our results highlight the general complexity of sibling effects, but broadly that elder siblings can influence the life-history trajectory of subsequent offspring. We also stress the importance of considering all life stages when evaluating sibling effects on life trajectories.

Denombreux mammifères grandissent en fratrie, et les interactions au sein de lafratrie peuvent influencer le phénotype et la valeur sélective des jeunes.Parmi ces interactions, la compétition entre frères et sœurs d'âges différentspeut entraîner des coûts de reproduction et de survie pour le/la plus jeune,tandis que les interactions coopératives améliorent la reproduction et lasurvie du/de la plus jeune. Cependant, nous avons encore peu de connaissancessur l'influence de la fratrie sur la trajectoire de vie des frères et sœursplus jeunes, en particulier chez les mammifères longévifs. Grâce àun jeu de données démographique multigénérationnel d'éléphants d'Asiesemi-captifs, nous avons pu étudier comment la présence d'un frère aînéou d'une sœur aînée influence le sexe, la survie jusqu'à l'âge de cinqans, la masse corporelle, la reproduction (i.e. l'âge de première reproductionet le succès reproductif sur toute la vie) et la survie à long terme du jeunesuivant. Nousobservons que les frères et sœurs aînés ont des effets hétérogènes sur lestraits d'histoire de vie du jeune suivant et ce, en fonction de leur présence,et du sexe du jeune suivant (appelé focal). Dansl'ensemble, la présence d'un frère aîné oud'une sœur aînée augmente fortement la survie à long terme du jeune focal parrapport à leur absence. Cependant, il est à noter que les sœurs aînées ont unimpact plus important que les frères ainés sur le frère focal. Les femellesfocales présentent une survie à long terme plus élevée et un âge de premièrereproduction plus précoce lorsqu'elles sont élevées avec une sœur aînée plutôtqu'un frère. Les mâles focaux élevés avec une grande sœur plutôt qu'un grandfrère présentent une survie plus faible mais un poids corporel plus élevé. Nousn'avons détecté aucun effet des frères aînés ou sœurs aînées sur le sexe, la survie jusqu'àl'âge de cinq ans et le succès reproducteur sur toute la vie du jeune focal. Nosrésultats mettent en évidence la complexité des effets de la fratrie et, lefait que les frères et sœurs plus âgés peuvent influencer la trajectoire ducycle de vie des jeunes suivant. Nous soulignons également l'importance deconsidérer toutes les étapes de la vie lors de l'évaluation des effets de lafratrie sur les trajectoires de vie.

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India has an unenviable reputation as one of the world's most gender disparate countries. Previous studies of sex bias in childhood have shown large differences between Indian boys and girls in immunization and curative healthcare, but little difference in health status as indicated by anaemia and stunting. India has changed rapidly in past decades, hence we reappraise the situation with the National Family Health Survey-4 (2015-16). We found no evidence of sex differentials in immunization coverage but a small degree of discrimination in favour of boys in medical treatment for common symptoms of infection. This discrimination was no greater in the North and Central regions of India, where severe excess mortality among female children persists. Sex differences in anaemia and stunting were small, with no regional pattern. We found no evidence that healthcare or health status of girls was influenced by the presence of other daughters in the family.

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Previous research has revealed that fetuses detect and respond to extrauterine stimuli such as maternal movement and speech, but little attention has been cast on how fetuses may directly influence and respond to each other in the womb. This study investigated whether motor activity of E20 rat fetuses influenced the behavior of siblings in utero. Three experiments showed that; (a) contiguous siblings expressed a higher frequency of synchronized movement than noncontiguous siblings; (b) fetuses that lay between two siblings immobilized with curare showed less movement relative to fetuses between saline or uninjected controls; and (c) fetuses between two siblings behaviorally activated by the opioid agonist U50,488 also showed less activity and specific behavioral changes compared to controls. Our findings suggest that rat fetuses are directly impacted by sibling motor activity, and thus that a rudimentary form of communication between siblings may influence the development of fetuses in utero.

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BACKGROUND: Prader-Willi syndrome (PWS), a complex multisystem genetic disorder, is characterised by developmental abnormalities leading to somatic and psychological symptoms. Symptoms of PWS include infantile hypotonia and failure-to-thrive, followed by life-long hyperphagia, developmental delays and moderate-to-severe behavioural problems and several physical problems that impact health. This study examined the effects of caring for a child diagnosed with PWS on the mothers and unaffected siblings. We assessed overall family functioning, the mothers' psychological health, the psychosocial and behavioural functioning of siblings, and the quality of life of siblings. METHODS: Participants included 12 mothers and 13 siblings of a child with genetically confirmed PWS. Self-report measures administered to the mothers evaluated overall family functioning (PedsQL - Family Impact Module), the mothers' psychological health (Brief Symptom Inventory), and the mothers' perception of the sibling's quality of life (PedsQL - Parent Proxy). Self-report measures administered to the siblings evaluated their perceived quality of life (PedsQL) and symptoms of post-traumatic stress disorder (PTSD) (UCLA PTSD Index). RESULTS: Families/mothers/siblings with children with PWS showed poorer perceived quality of life compared with general inpatient and outpatient samples of children with complex health conditions. Families/mothers/siblings with children with PWS reported difficulties in family functioning, communication problems, and an increased number of conflicts. They appeared to be experiencing significant behavioural distress symptoms, with higher than average levels of depression and feelings of isolation, anger and worry. Ninety-two per cent of the siblings indicated moderate-to-severe symptoms of PTSD. Compared with normative populations, siblings demonstrated poorer quality of life, with mothers perceiving more significant deficits in the sibling. CONCLUSION: This study reaffirms that PWS affects the entire family system. Mothers and siblings would benefit from psychosocial support due to the multiple challenges of living with and caring for a child/young adult with PWS.

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