This study explores directional selection on physical and psychosocial phenotypes in Eastern Eurasian populations, utilizing a dataset of 1245 ancient genomes. By analyzing polygenic scores (PGS) for traits including height, educational attainment (EA), IQ, autism, schizophrenia, and others, we observed significant temporal trends spanning the Holocene era. The results suggest positive selection for cognitive-related traits such as IQ, EA and autism spectrum disorder (ASD), alongside negative selection for anxiety and depression. The results for height were mixed and showed nonlinear relationships with Years Before Present (BP). These trends were partially mediated by genetic components linked to distinct ancestral populations. Regression models incorporating admixture, geography, and temporal variables were used to account for biases in population composition over time. Latitude showed a positive effect on ASD PGS, EA and height, while it had a negative effect on skin pigmentation scores. Additionally, latitude exhibited significant nonlinear effects on multiple phenotypes. The observed patterns highlight the influence of climate-mediated selection pressures on trait evolution. Spline regression revealed that several polygenic scores had nonlinear relationships with years BP. The findings provide evidence for complex evolutionary dynamics, with distinct selective pressures shaping phenotypic diversity across different timescales and environments.

Both peer influences and genetics have been linked to gaming addiction (GA) in adolescents and young adults. This study examined the gene-environment interplay (gene-environment correlation [rGE] and gene-environment interaction [G x E]) between close friends’ gaming (CFG) and GA among South Korean twins. A total of 1462 twins aged 15–29 years (mean = 22.63 ± 2.8 years) completed an online survey that included a 20-item GA measure and a single item assessing CFG. Bivariate Cholesky model-fitting analysis was conducted to examine evidence for rGE in the relationship between GA and CFG. Bivariate G x E model-fitting analysis was performed to determine evidence for G x E effects. A significant genetic correlation (rg = .37; 95% CI [0.24, 0.49]) between GA and CFG supported the role of gene-environment correlation, suggesting that individuals with a genetic predisposition for GA may selectively associate with peers who frequently engage in gaming. The model testing G x E effects indicated that environment-environment interaction was present in the relationship between CFG and GA, such that CFG increased nonshared environmental effects on GA. This pattern provided evidence for peer socialization effects, wherein peers influence the development of GA independently of genetic risk.

Research is only beginning to shape our understanding of eating disorders as metabolic-psychiatric illnesses. How eating disorders (EDs) are classified is essential to future research for understanding the etiology of these severe illnesses and both developing and tailoring effective treatments. The gold standard for classification for research and diagnostic purposes has primarily been and continues to be the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). With the reconceptualization of EDs comes new challenges of considering how EDs are classified to reflect clinical reality, prognosis and lived experience. In this article, we explore the DSM-5 method of categorical classification and how it may not accurately represent the fluidity in which EDs present themselves. We discuss alternative methods of conceptualizing EDs, and their relevance and implications for genetic research.

Prior studies report a decline in male twin live births during economically stressful periods, presumably owing to higher selection in utero against frail male gestations, yet no study has examined the natural corollary: whether provision of economic support increases rates of male twin births. We examined whether male twin live births increase following income gains from the Alaska Permanent Fund Dividend (PFD)—the longest running unconditional cash transfer program in the US. We obtained the monthly volume of male (and female) twin and singleton live births, from January 1980 to December 2019, from Alaska’s Department of Health. Data on PFD timing and payment amounts came from Alaska’s Department of Revenue. We used time-series analyses to gauge whether the odds of male twin live births increase within 2−6 months following PFD receipt, controlling for autocorrelation. Results suggest that for every $1000 increase in PFD payments, the odds of male twin live births increase by 0.002 (p < .05) three months following PFD disbursement. This corresponds with 50 additional (individual) male twin live births statistically attributable to the cumulative PFD amount disbursed over our study period. Income gains through the PFD may correspond with reduced male-specific selection in utero in Alaska.

Previous observational studies have suggested an association between natural hair color and the risk of endometriosis; however, the causal relationship remains unclear. Here, we conducted a two-sample Mendelian randomization (MR) study to evaluate the potential causal link between natural hair color and endometriosis using 428 single nucleotide polymorphisms (SNPs) as genetic instruments derived from a genomewide meta-analysis comprising over 4511 cases and 227,260 controls of European ancestry. Our findings indicate that dark brown hair is associated with a decreased risk of developing endometriosis (dark brown IVW OR: 0.844, 95% CI [0.725, 0.984], p < .05). Conversely, dark hair color and lighter hair colors (red, blonde, and light brown) did not demonstrate a significant association with endometriosis risk (dark IVW OR: 0.568, 95% CI [0.280, 1.15], p = .117; red IVW OR: 1.058, 95% CI [0.719, 1.558], p = .77; blonde IVW OR: 1.158, 95% CI [0.886, 1.514], p = .28; light brown IVW OR: 1.306, 95% CI [0.978, 1.743], p = .07). These results provide compelling MR evidence supporting a causal association between natural hair color and endometriosis risk. Our findings underscore the need for larger scale studies and randomized controlled trials to delineate the biological mechanisms driving the association between hair color and endometriosis.

This study aimed to create a risk prediction model with artificial intelligence (AI) to identify patients at higher risk of postpartum hemorrhage using perinatal characteristics that may be associated with later postpartum hemorrhage (PPH) in twin pregnancies that underwent cesarean section. The study was planned as a retrospective cohort study at University Hospital. All twin cesarean deliveries were categorized into two groups: those with and without PPH. Using the perinatal characteristics of the cases, four different machine learning classifiers were created: Logistic regression (LR), support vector machine (SVM), random forest (RF), and multilayer perceptron (MLP). LR, RF, and SVM models were created a second time by including class weights to manage the underlying imbalances in the data. A total of 615 twin pregnancies were included in the study. There were 150 twin pregnancies with PPH and 465 without PPH. Dichorionity, PAS, and placenta previa were significantly higher in the PPH-positive group (p = .045, p = .004, p = .001 respectively). In our model, LR with class weight was the best model with the highest negative predictive value. The AUC in our LR with class weight model was %75.12 with an accuracy of 70.73%, a PPV of 47.92%, and an NPV of 85.33% in our data. Although the application of machine learning to create predictive models using clinical risk factors and our model’s 70% accuracy rate are encouraging, it is not sufficient. Machine learning modeling needs further study and validation before being incorporated into clinical use.

The International Society for Twin Studies (ISTS) held its 19th scientific congress in Assisi, Italy, from September 26 to 28, 2024. This prestigious event, which was the seventh joint meeting with the World Congress on Twin Pregnancy, brought together researchers from various fields, including psychology, biology and medicine. Representatives from ICOMBO (the International Consortium of Multiple Birth Organisations), which supports multiple-birth families worldwide, were also in attendance. Many twin researchers consider this event to be the highlight of their professional year, as it brings together experts and parents alike to discuss the latest advancements in twin studies.

Giving twins similar names places them at increased risk for mixed credit reports as they enter young adulthood and beyond. Attorneys specializing in this area of the law are often required to manage lawsuits againt the agencies responsible for such errors. This overview is followed by summaries of twin research and reports of treating twins with central nervous system infection, twins with COVID-19, and twins with septal aneurism, as well as a review of the comparative outcomes of twins born via assisted reproduction versus natural conception and a tribute to the late Dr Helen E. Fisher. Human interest items include a twins’ rally for Israeli twins held hostage in Gaza, a tribute to the founding member of the National Mothers of Twins Clubs (now Multiples of America), a quadruplet birth, an identical twin politician, and identical twin actresses.