Teenagers who drank more sugar-sweetened beverages were more likely to screen positive for depression and anxiety over three years, according to an Australian study. Those who ate more fruit were less likely to. The early findings suggest everyday food choices may matter for adolescent mental health, but they do not prove that diet changes anything.
Who Was Followed, and How
Researchers led by L. Davidson tracked 6,537 students across 71 schools in New South Wales, Queensland and Western Australia. The average age at the start was about 13, and roughly half were girls. All had earlier taken part in the Health4Life school trial. The work appears in the journal Child and Adolescent Mental Health.
Each year for three years, starting in Grade 7, the students completed digital surveys on daily fruit, vegetable and sugary-drink intake. A serving of fruit was set at 150 grams and a serving of vegetables at 75 grams. Drinks were counted in cups of soft drink, sports drink or cordial, including lemonade, Coke and Gatorade.
The mental health outcomes were screening results, not diagnoses. Depression was scored on eight items of the Patient Health Questionnaire-Adolescent, leaving out the question on suicidal thoughts. Anxiety was measured with a 13-item pediatric scale from the Patient-Reported Outcomes Measurement Information System. Students who already met a threshold at baseline, or lacked baseline data, were excluded so the analysis could focus on symptoms that emerged during follow-up. The models adjusted for sex, age, physical activity, trial group and family affluence.
What the Numbers Showed
Higher sugary-drink intake was tied to a greater risk of crossing the threshold for both conditions. The link appeared in boys and girls, with larger estimates in boys, especially for anxiety. The analysis did not establish whether that sex difference was statistically meaningful.
Fruit pointed the other way. Each extra daily serving was associated with a 13% lower risk of depression and a 7% lower risk of anxiety. Vegetables showed no significant association. When the data were split by sex, the fruit and anxiety link was no longer statistically significant. The sugary-drink result was the more consistent of the two.
The authors proposed that inflammatory markers or hormones such as cortisol might play a part in how sugary drinks affect mood. The study did not test those mechanisms, and sugary drinks may simply travel with other habits that were not fully measured. In analyses that dropped participants with missing data, fruit lost its significant links to anxiety overall and to depression in boys.
What It Cannot Say
The design was observational, diet was self-reported, and unmeasured factors could play a role, so the study cannot show that changing what teenagers drink prevents mental disorders. Earlier research mostly looked at diet and mood at a single moment, and studies that followed young people longer have reached different conclusions. The team called for work that tests cause and biology, and for work on protein, healthy fats, whole grains and ultra-processed foods, as well as on family history and household eating patterns.
The encouraging part is that diet can be changed. If later studies confirm the pattern, school programs and family habits, such as keeping fewer sugary drinks at home and offering fruit, could become part of prevention. Families worried about a teenager’s mood or eating should talk to their doctor.
Sources
- Fruit and sugary drinks stood out in a three-year study of teenage mental health
- Sweetened beverage
- Berkeley voters to decide on measure that would double city's soda tax
Photo: Harrison Keely (CC BY 4.0)
