Association between Chinese only-child university students’ psychological symptoms and lifestyle behaviors

Only children in China have been reported to experience greater psychological distress and engage in less healthy behaviors compared to their peers with siblings. This study aimed to investigate associations between physical activity, sedentary behaviors, dietary habits, sleep duration, and psychological symptoms among only-child university students in China. A cross-sectional study was conducted in 2023 among university students aged 18–22 years from four provinces in China. Data were collected using self-reported questionnaires on demographic characteristics, consumption of carbonated drinks, and frequency of fast food or takeout. Psychological symptoms, sleep duration, physical activity, and sedentary behaviors were assessed using the Depression, Anxiety, and Stress Scale-21 (DASS-21), Pittsburgh Sleep Quality Index (PSQI), and International Physical Activity Questionnaire (IPAQ), respectively. Propensity Score Matching (PSM) was applied to control confounding factors. Univariate analyses employed independent-sample t-tests and chi-square tests. Multiple mediation analyses were conducted to examine whether lifestyle behaviors mediated the association between only-child status and psychological symptoms. Binary logistic regression was used for multivariate analysis to explore associations between psychological symptoms and lifestyle behaviors among only children and non-only children. Additionally, restricted cubic spline analyses were conducted to further assess linear and nonlinear associations between the number of healthy behaviors and psychological symptoms. A total of 8,131 Chinese university students participated in this study. The prevalence of psychological symptoms was significantly higher among only children compared to students with siblings (P < 0.001). After PSM, 2,118 matched pairs of only children and non-only children were included, and the comparison of psychological symptoms between these two groups remained significant. Furthermore, only children exhibited significantly higher proportions of unhealthy lifestyle behaviors compared to their peers with siblings (P < 0.05). Multiple mediation analysis further revealed that several lifestyle behaviors mediated the association between only-child status and psychological symptoms (P < 0.05). Multivariate logistic regression analysis indicated that unhealthy lifestyle behaviors were positively associated with psychological symptoms among only children. Healthy beverage consumption habits, adequate sleep duration, and reduced sedentary time were associated with 17–44% lower odds of depression symptoms (DS), 24–50% lower odds of anxiety symptoms (AS), and 30–54% lower odds of stress symptoms (SS) among only children. Moreover, a dose-response relationship analysis demonstrated that those reporting four healthy behaviors had 57% significantly lower odds of DS; three to five healthy behaviors had 69%-83% significantly lower odds of AS, and 57%-75% lower odds of SS. The restrictive cubic analysis was furtherly showed the linear trend association between them. Only children exhibited more severe psychological symptom and more unhealthy lifestyle behaviors compared to peers with siblings. A significant dose-response relationship was observed between the number of healthy lifestyle behaviors and the reduction of psychological symptoms among only-child university students.