This study examined the influence of personality and negative life events during adolescence on depression in young adulthood, and the extent to which common genetic and environmental influences contributed to these associations. The data come from a Norwegian population based twin sample (N = 3,394). Depression was predicted by higher neuroticism and loneliness, as well as lower sense of coherence, self-efficacy, and resilience. Additionally, weak positive associations were found between negative life events and depression. Common genetic influences accounted for most of the phenotypic associations between depression and both personality and negative life events. The findings emphasize the importance of assessing personality characteristics early in adolescence, as they may serve as vulnerabilities for the development of depression later in life.

The Serbian Twin Advanced Registry (STAR), established in 2014, is a multigenerational resource for studying genetic, environmental, and epigenetic influences on behavior and development. STAR currently includes more than 9000 participants, extending the classical twin design to parents and siblings and enabling fine-grained modeling of genetic inheritance, cultural transmission, and shared environments. Methodological innovations include experimental procedures, virtual reality paradigms, and longitudinal, multi-informant assessments from childhood to adulthood, combined with molecular data collection. Published findings highlight heritable structures in executive functions, personality, and psychopathology, alongside environmentally shaped differences in behaviors such as aggression. Epigenetic studies have demonstrated associations between COMT promoter methylation and impulsivity-related traits, while ongoing genomewide analyses aim to identify environmentally mediated methylation variability. By integrating advanced methodologies with open science practices, STAR provides a sustainable platform for behavioral genetics in Serbia and contributes to international research on adaptation and psychopathology across the lifespan.

The triglyceride-glucose (TyG) index is a reliable composite marker of insulin resistance, which holds important clinical significance. Existing studies have predominantly focused on identifying TyG index-related genetic loci and single-nucleotide polymorphism (SNP)-based polygenic risk scores, however, the overall contribution of genetic factors to TyG index variation at the population level is still unclear. To address this gap, we conducted a classic twin study using data from the Qingdao Twin Registry in China. The study included 381 middle-aged and older Chinese twin pairs (241 monozygotic and 140 dizygotic), comprising 370 males and 392 females. The median age of participants was 50 (interquartile range: 12) years. Structural equation modeling was applied to estimate the heritability of the TyG index after adjusting for age, gender, and body mass index (BMI). Model fitting identified the AE model as the best-fitting one. Additive genetic effects (A) accounted for 60.48% (95% CI [52.46, 67.24]) of the total variance, while unique environmental effects (E) explained 39.52% (95% CI [32.76, 47.54]). A sex-limitation model was subsequently used to test for sex differences in TyG. The results showed that heritability was higher in females (67.2%) than in males (54.0%). This twin-based study provides robust evidence for a moderate‑to‑high heritability of the TyG index in a Northern Chinese population, underscoring the substantial genetic contribution to this composite insulin resistance marker. Notably, the sex difference in heritability reflects larger unique environmental variance in males, highlighting the differential contribution of environmental factors across sexes.

This study compared mental health problems and psychiatric treatment experiences between mothers of twins and mothers of singletons, controlling for assisted reproductive technology (ART), perceived family support (PFS), and demographic covariates. Participants were 1592 South Korean mothers, including 853 mothers of singletons (M = 36.6 years, SD = 3.6) and 739 mothers of twins (M = 38.3 years, SD = 4.9), who completed an online survey assessing the General Health Questionnaire (GHQ), psychiatric treatment experience (PTE), PFS, ART use, and demographic factors. Hierarchical regression, analysis of covariance (ANCOVA), and logistic regression analyses were conducted with GHQ as the outcome variable. PTE was analyzed both as a dependent variable and as an independent variable. ART use significantly predicted GHQ scores beyond PFS, PTE, and demographics in both groups. After adjusting for all covariates, mothers of twins had higher GHQ scores than mothers of singletons, although the effect size was small (Cohen’s d = 0.16). Logistic regression revealed that mothers of twins were more than twice as likely to have received psychiatric treatment compared to mothers of singletons (odds ratio = 2.5, 95% CI [1.8, 3.4]). These results indicate that mothers of twins experience greater mental health challenges than mothers of singletons, indicating the importance of tailored mental health screening, prevention, and intervention programs for this vulnerable group.

Establishing causality in nutritional science is difficult. Human diets are complex, and individuals vary substantially in how they respond to dietary exposures. The nutrition literature mostly relies on observational studies, which are vulnerable to confounding and measurement error. Twin-based randomized controlled trials (RCTs), especially the co-twin control design, offer a compelling methodological solution to many of these challenges. This design enables researchers to distinguish genetic from environmental influences on health outcomes. The present scoping review was conducted to systematically map twin RCTs in nutrition science, evaluate their methodological approaches, and identify gaps and opportunities for future research. A comprehensive search across clinical trial registries and electronic databases yielded only 13 eligible studies, demonstrating that co-twin randomized dietary interventions remain rare relative to standard study designs using nontwins or twins assigned to the same arm. The interventions used in these eligible RCTs could be classified into four groups: dietary pattern interventions, nutrient- or supplement-based interventions, dietary component modification, and behavioral or multimodal interventions. This limited number of studies may be explained by recruitment challenges and concerns about generalizability. Greater international collaboration, standardized trial protocols, and integration of emerging technologies could expand the utility of twin designs in nutrition science.

Twin-to-twin transfusion syndrome (TTTS) affects 10–15% of monochorionic diamniotic (MCDA) twin pregnancies and is associated with high perinatal mortality if left untreated. Selective Fetoscopic Laser Photocoagulation (SFLP) is the current standard of care for advanced-stage TTTS. This retrospective cohort study aimed to assess survival outcomes following SFLP and evaluate the learning curve associated with its implementation. It included 300 MCDA twin pregnancies with TTTS treated by SFLP from October 2018 to December 2024. Patients were chronologically divided into three equal groups (n = 100 per group) based on the order of procedure to assess outcome trends over time. Primary outcome was dual survival at birth; secondary outcomes included survival of at least one fetus, gestational age at delivery, birth weight, and neonatal complications. Multivariable logistic regression was used to assess clinical and procedural factors associated with dual survival, while CUSUM analysis was employed to evaluate the learning curve. Among 300 cases, dual survival was achieved in 57% of pregnancies. In multivariable logistic regression, clinical factors, including Quintero stage, placental orientation, and gestational age, were not significantly associated with outcomes (p > .05). The treatment cohort remained the sole independent predictor of survival, with significantly lower odds of success in Group 1 (OR 0.041; 95% CI [0.004, 0.429]) and Group 2 (OR 0.051; 95% CI [0.005, 0.492]) compared to Group 3 (p < .01). CUSUM analysis demonstrated that procedural competence, defined by sustained adequate survival rates, was achieved after the 141st procedure. This study demonstrates improved survival outcomes in TTTS cases treated with SFLP over time, confirming a significant institutional learning curve. The findings highlight the importance of surgical experience and procedural standardization. In resource-limited settings, establishing structured training and mentorship is essential to optimize outcomes and safely expand access to fetal therapy.

This study aims to explore the significance of discrepancies in crown-rump length (CRL) and abnormal cord insertion in predicting selective fetal growth restriction (sFGR) in monochorionic (MC) twin pregnancies. Special attention was paid to determining the potential value of these factors in early pregnancy for predicting sFGR. A retrospective analysis included 131 pregnant women diagnosed with MC twin pregnancies. CRL was measured using a GE E8 color Doppler ultrasound instrument. Groups were compared based on the discrepancy in CRL (≥6 mm difference group, n = 26; <6 mm normal group, n = 105) and the presence of abnormal cord insertion (abnormal group, n = 27; normal group, n = 104). The study found no significant association between CRL discrepancy and postnatal birth-weight discordance suggestive of sFGR (p > .05). In contrast, abnormal cord insertion was significantly associated with an increased occurrence of sFGR-related outcome (p < .001). Specifically, sFGR-related outcome occurred in 12 of 27 cases (44.4%) in the abnormal cord insertion group, compared with 7 of 104 cases (6.7%) in the normal cord insertion group. In this retrospective MC twin cohort, abnormal cord insertion was associated with an increased risk of postnatal birth-weight discordance suggestive of sFGR, whereas CRL discrepancy showed limited discriminative ability. Because of the retrospective design, limited number of outcome events, and use of postnatal rather than standardized antenatal Doppler-based sFGR criteria, these findings should be interpreted as exploratory and require validation in larger prospective studies.

Neonates are highly susceptible to infection, a major cause of neonatal death, given their immature immune system. Comprehensive studies examining multiple immune-response-related proteins in relation to neonatal infection are scarce. We conducted a nested case-control study within the Shenzhen Baoan Birth and Twin (SZBBTwin) cohort, measuring 92 immune-response-related proteins in cord plasma of 149 twins (including 34 discordant twin pairs) with proximity extension assay. All twins were followed for clinical diagnoses of infection from birth until 27 days of age. Wilcoxon rank-sum test was used to determine differentially abundant proteins (DAPs) between infected and noninfected neonates, the predictive performance of which was evaluated by receiver operating characteristic curves, and their functions and pathways were annotated through enrichment analysis. Logistic regression was used to assess the associations between levels of proteins and risk of neonatal infection. Finally, five DAPs (ITGA11, FCRL6, DDX58, SH2D1A, and EDAR) were identified for neonatal infection, and the area under the curve of the five DAPs achieved 0.835 for infection prediction. Enrichment analysis indicated that five DAPs were mainly involved in immune function and cell binding, and they were mainly enriched in the nuclear factor kappa-B pathway. A higher level of ITGA11 was associated with an increased risk of neonatal infection in all twins (OR 3.00; 95% CI [1.33, 6.78]) and discordant twin pairs (OR 5.50; 95% CI [1.20, 25.23]). In conclusion, multiple immune-response-related proteins in cord plasma, particularly ITGA11, are associated with the risk of neonatal infection in twins.

A pair of young monozygotic male twins affected with Feingold syndrome were briefly described in previous issues of Twin Research and Human Genetics. An opportunity to meet the twins and their mother occurred in March 2026. An overview of the condition and interview with the twins’ mother is presented, as are implications for future research and practice. Next, research summaries of pseudoamonoamniotic twins, selective fetal growth restriction in monoamniotic twins, twin authorship attribution, and twins discordant for clubfoot are provided. This article concludes with human interest stories involving twins with different fathers, biological relatedness in a married couple, the birth of identical quadruplets, and twins switching places.