Factors affecting sibling bullying and its association with self-esteem and depression in middle school students

Sibling bullying is an unwanted aggressive behavior of a sibling that is associated with peer bullying and emotional problems. However, the prevalence of sibling bullying, the factors that affect this condition, and its impact on depression and self-esteem are understudied, especially in Thailand. This study aims to examine the prevalence of sibling bullying, factors that affect sibling bullying, and its association with self-esteem and depression during the pandemic. From January to February 2022, a cross-sectional study was conducted in grades 7-9 (age 12-15 years) who had at least one sibling. Demographic characteristics, sibling bullying, self-esteem, and depression were collected using the revised Olweus bully/victim questionnaire, the Rosenberg self-esteem scale, and Patient Health Questionnaire-9, respectively. Binary logistic regression was analyzed to determine associations between sibling bullying and outcomes. Of 352 participants (30.4% female), 92 (26.1%) were victims and 49 (13.9%) were bullies of sibling bullying in the previous 6 months. Factors associated with an increased risk of being victims included female (OR = 2.46; 95%CI 1.34-4.53), peer victimization (OR = 12.99; 95%CI 5.27-32.04), domestic violence (OR = 4.48; 95%CI 1.68-11.95), and perpetrating sibling bullying (OR = 9.81; 95%CI 4.62-20.81). Factors associated with an increased risk of depression were female (OR = 2.59; 95%CI 1.57-4.26), sibling bullying victimization (OR = 2.08; 95%CI 1.22-3.56), physical abuse (OR = 9.50, 95%CI 1.13-79.71) and domestic violence (OR = 3.44; 95%CI 1.40-8.45).  Conclusion: Sibling bullying was not uncommon in Thai young adolescents and was associated with female, peer bullying, domestic violence, and depression. Such associations should be identified early so preventive measures and management could be properly implemented. What is Known: • Sibling bullying increases the risk for engaging in peer bullying, aggressive behaviors, violence, and emotional difficulties during life course trajectories. • Victims of sibling bullying are at increased risk of depression, anxiety, mental distress, self-harm, and decreased well-being. What is New: • The rate of sibling bullying in Thai middle school students, even during the pandemic, was comparable to previous studies of different cultural backgrounds without the pandemic. • Victims of sibling bullying were associated with female sex, peer victimization, domestic violence, perpetrating sibling bullying, and depression. Perpetrating sibling bullying was also associated with bullies in cyberbullying.