Type-, dose-, and subgroup-specific associations of dairy intake with depressive and anxiety symptoms among middle school students.

Abstract

Background: Depression and anxiety are major public health concerns among adolescents. Dairy products are important components of adolescent diets, but evidence on the associations of different dairy intake patterns with mental health symptoms remains limited. This study examined the associations of six dairy intake variables with depressive and anxiety symptoms among middle school students.

Methods: This cross-sectional study included 135,138 middle school students in China. Dairy intake was assessed using six variables: frequencies of milk, yogurt, milk powder, and cheese/cheese cube intake; daily amount of milk, yogurt, and milk powder; and daily amount of cheese/cheese cubes. Depressive and anxiety symptoms were assessed using the Center for Epidemiologic Studies Depression scale and the Generalized Anxiety Disorder scale, respectively. Multivariable linear regression models, restricted cubic spline analyses, and interaction analyses by gender and urban-suburban context were conducted. The secondary analysis was approved by the Medical Ethics Committee of the Shandong Center for Disease Control and Prevention (Approval No. SDJK(K)2025-057-01).

Results: Daily milk intake was reported by 27.5% of students, whereas daily yogurt, milk powder, and cheese/cheese cube intake were less common. Higher frequencies of milk and yogurt intake were associated with lower depressive and anxiety symptom scores. Compared with students who never consumed milk, daily milk consumers had lower depressive symptoms (β = -2.30, 95% CI:-2.50 to -2.10) and anxiety symptoms (β = -0.90, 95% CI:-0.99 to -0.81). The associations for milk powder, cheese/cheese cubes, and total dairy amount were more complex. Restricted cubic spline analyses suggested nonlinear associations, and interaction analyses indicated that several associations differed by gender and urban-suburban context.

Conclusions: Dairy intake was differentially associated with depressive and anxiety symptoms among middle school students. More frequent milk and yogurt intake showed relatively consistent inverse associations with symptom scores, whereas associations for milk powder, cheese/cheese cubes, and amount-based dairy measures were less consistent and, for some measures, sensitive to model specification. These findings should be interpreted as observational associations and warrant further investigation in longitudinal studies with more detailed dietary assessment.