Abstract
OBJECTIVE: Sugar is an essential part of the daily diet but poses multiple health risks. Previous studies have neglected the association between specific sugar subtypes and mental health. This study aimed to systematically evaluate the associations between ten subtypes of sugar and three mental disorders: depression, anxiety, and self-harm. DESIGN, SETTING, AND PARTICIPANTS: This cohort study analyzed 169,776 participants from the UK Biobank (recruited from 2006 to 2010), who completed at least one dietary questionnaire collection through the Oxford WebQ. Data analysis was conducted from November 2024 to March 2025. EXPOSURES: Sugar intake was calculated based on the Oxford WebQ data. MAIN OUTCOMES AND MEASURES: Cox proportional hazards regression models were used to assess the hazard ratios (HR) of sugar intake on depression, anxiety, and self-harm, and restricted cubic spline (RCS) regressions were conducted to evaluate the significance of dose-response relationships and nonlinear associations. RESULTS: A total of 6,637 cases of depression, 6,160 cases of anxiety, and 374 cases of self-harm were identified, with a median follow-up time of 10.54 years. Compared to low intake, high intake of total sugars, free sugar, lactose, non-milk extrinsic sugars, and sucrose was associated with an increased risk of depression (HR = 1.26, 95% CI [1.18-1.33], 1.23 [1.16-1.30], 1.15 [1.08-1.22], 1.24 [1.17-1.32], and 1.33 [1.25-1.41]), anxiety (1.20 [1.13-1.28], 1.22 [1.14-1.29], 1.16 [1.09-1.23], 1.23 [1.15-1.31], and 1.28 [1.21-1.37]), and self-harm (1.37 [1.08-1.75], 1.35 [1.06-1.72], 1.64 [1.27-2.11], 1.45 [1.14-1.84], and 1.37 [1.08-1.75]). In contrast, moderate glucose intake was associated with a reduced risk of depression and anxiety (0.93 [0.88-0.99], and 0.92 [0.86-0.98]). These associations were more pronounced in individuals with obesity. The dose-response relationship curves between sugar subtypes and mental disorders generally followed a U-shaped or J-shaped pattern, emphasizing the crucial role of specific sugar subtypes and intake ranges in influencing disease risk. CONCLUSIONS AND RELEVANCE: Excessive sugar consumption elevates the risks of depression, anxiety, and self-harm, whereas moderate intake demonstrates protective effects, particularly in obese populations. These U/J-shaped dose-response relationships inform our proposed sugar intake guidelines for mental health management.