Fruit and sugary drinks stood out in a three-year study of teenage mental health, with Australian researchers finding that daily consumption of sugar-sweetened beverages increases the odds of meeting screening thresholds for depression and anxiety among adolescents.
The study followed 6,537 adolescents with an average age of 13 from 71 schools across New South Wales, Queensland and Western Australia for three years. Participants reported their daily intake of fruit, vegetables and sugar-sweetened beverages via digital surveys each year. Higher consumption of sugar-sweetened beverages was associated with a greater risk of meeting screening thresholds for both depression and anxiety, with the association being numerically stronger for anxiety among male students.
Study Design and Participant Profile
Researchers investigated whether fruit, vegetable and sugar-sweetened beverage consumption was associated with meeting screening thresholds for anxiety and depression over three years among the adolescent cohort. Depression and anxiety outcomes were determined based on binary cut-offs in validated symptom scales, rather than clinical diagnoses. To assess depression, the team evaluated eight items of the Patient Health Questionnaire-Adolescent (PHQ-A-8), excluding assessment of thoughts of suicide. Anxiety levels were evaluated using the 13-item Patient-Reported Outcomes Measurement Information System Anxiety-Pediatric (PROMIS-AP) scale. Participants attended secondary schools in New South Wales, Queensland, and Western Australia, and had previously taken part in the Health4Life trial. They completed digital surveys at baseline (Grade 7, 12-13 years old) and again after one, two, and three years to report their daily intake of vegetables, fruit, and sugar-sweetened beverages.
Key Mental-Health Findings Linked to Sugary Drinks
Higher sugar-sweetened beverage consumption was associated with a greater risk of meeting screening thresholds for both depression and anxiety. The association was numerically stronger for anxiety among male students. Sugar-sweetened beverages are defined as beverages sweetened with added sugars such as high-fructose corn syrup, sucrose, and honey, often called “liquid candy.” Consumption of sugar-sweetened beverages is linked to weight gain, cardiovascular disease, and unhealthy lifestyle behaviors, underscoring broader health concerns. Because diet is modifiable, the study suggests that reducing sugar-sweetened beverage intake could be an early prevention strategy for adolescent mental disorders. The study builds on prior research that mostly captured diet and mental health at a single point, highlighting the value of longitudinal data.
Protective Effect of Fruit Intake
Greater fruit intake was linked to lower risks of meeting screening thresholds for depression and anxiety. Each additional daily serving of fruit reduced depression risk by 13% and anxiety risk by 7%. This inverse relationship remained consistent across the three-year follow-up period. Researchers noted that dietary habits established during childhood and adolescence may have lasting implications for mental well-being and could represent an important area for early prevention.
Practical Steps Families Can Take
Family-level interventions, such as limiting sugary drinks at home and encouraging fruit snacks, are practical steps derived from the findings. The researchers call for further longitudinal studies to clarify causal pathways between diet and mental health. As with any health-related observation, individuals should consult their doctor for personalised advice.
Geographic Scope of the Australian Study
The research included adolescents from secondary schools across three Australian states: New South Wales, Queensland, and Western Australia. Participants were drawn from 71 schools within these regions, ensuring a broad geographic representation. This multi-state design allowed researchers to capture diverse demographic and environmental influences on dietary habits and mental health outcomes.
The cohort consisted of 6,537 adolescents with a mean age of approximately 13 years at baseline, about half of whom were female. All participants had previously taken part in the Health4Life trial, a prior school-based health initiative. Their involvement in this earlier program facilitated consistent follow-up and data collection over the three-year study period.
Digital surveys were administered annually, beginning at Grade 7 (ages 12–13) and repeated after one, two, and three years. These surveys captured self-reported daily intake of fruit, vegetables, and sugar-sweetened beverages. The longitudinal approach enabled researchers to track changes in diet and mental health symptoms over time, strengthening the validity of the observed associations.
Expert Commentary and Future Research Directions
The study’s authors emphasize that “the evidence is not yet consistent” regarding how adolescent dietary patterns influence mental health, noting that many prior investigations have relied on single‑time‑point assessments. They point out that “studies that followed young people over longer periods have reached different conclusions,” underscoring the need for additional longitudinal work to reconcile these divergent findings.
Because diet is a modifiable risk factor, the researchers argue that “exploring associations between specific dietary factors and CMD risk could help healthcare providers develop interventions to prevent or delay CMD onset.” They suggest future investigations should move beyond binary screening thresholds to incorporate clinical diagnoses, examine biological mechanisms linking sugar intake to mood regulation, and test school‑based or community interventions that reduce sugary‑drink consumption while promoting fruit intake.
Overall, the authors call for “more research … to clarify this relationship,” highlighting the importance of larger, diverse cohorts and experimental designs that can establish causality rather than merely correlation.
Funding and Institutional Support
The study was conducted by researchers affiliated with Australian institutions and published in the journal Child and Adolescent Mental Health. Participants were drawn from the Health4Life trial, a prior school-based health initiative that facilitated longitudinal follow-up. The research involved 71 schools across New South Wales, Queensland, and Western Australia, leveraging existing infrastructure from the earlier program to ensure consistent data collection over the three-year period. This prior involvement in the Health4Life trial enabled efficient recruitment and retention of the adolescent cohort throughout the study duration.
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