Feasting on ultra-processed foods? New study links diet to surging depression rates

By Bhavana KunkalikarReviewed by Benedette Cuffari, M.Sc.May 17 2023

Previous studies on the global burden of disease indicate that depressive disorders are among the most common mental disorders and have the highest overall burden. One potential risk factor for depression that can be modified is poor diet quality.

In a recent study published in the Journal of Affective Disorders, researchers explore the association between the consumption of high amounts of ultra-processed foods and psychological distress.

Study: High ultra-processed food consumption is associated with elevated psychological distress as an indicator of depression in adults from the Melbourne Collaborative Cohort Study. Image Credit: Ekaterina Markelova / Shutterstock.com

About the study

The current study was registered with the Open Science Framework (OSF) registry and adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement and checklist. Over 41,000 individuals between the ages of 27 and 76 years were enrolled from Melbourne between 1990 to 1994. Nearly 25,000 of these individuals identified as female, with almost 99% of the study cohort between the ages of 40 and 69 years.

A higher number of migrants from Southern Europe were included in the study to increase the variety of diet and lifestyle experiences. The study cohort previously answered dietary and psychological distress questionnaires at baseline and at end of the study.

Of the 41,513 individuals initially recruited for the study, 28,240 attended the second follow-up visit. Among these, 24,674 completed both the dietary intake assessments at baseline and the psychological distress questionnaire at the second follow-up.

Baseline dietary data was gathered from participants who attended in-person clinics. Study participants self-administered a 121-item Food Frequency Questionnaire (FFQ) to evaluate their dietary intake. Additionally, the researchers calculated the average daily consumption of ultra-processed foods in terms of both energy and weight by converting the reported frequencies of consumption into grams using sex-specific food portion sizes and multiplying it by the daily frequency.

The Kessler Psychological Distress Scale (K10) was used to measure psychological distress during follow-up. K10 evaluates general psychological distress, with elevated K10 scores indicating the presence of typical mental illnesses.

Results

A total of 13,876 females and 9,423 males were included in the final analysis. Individuals who consumed the highest amount of ultra-processed foods were more likely to be born in New Zealand or Australia and living alone. These individuals were also less likely to report a tertiary education, be in a married or de facto relationship, be the least disadvantaged, and engage in high physical activity levels. Higher consumption of ultra-processed foods was associated with lower intake of protein, fiber, and saturated fat, as well as reduced total energy and vegetable and fruit intake.

Model 1 found that individuals who consumed the highest quartile of ultra-processed food adjusted for energy had a 1.14-fold higher likelihood of experiencing elevated psychological distress as compared to those who consumed the lowest quartile. In the main multivariable analysis, after adjusting for potential covariates, the association rose to a 1.23-fold higher likelihood of increased psychological distress.

The fourth and highest quartile of energy-adjusted ultra-processed food consumption showed a significant difference as compared to the reference quartile across all models. A threshold effect was observed, which indicated that the link between consuming ultra-processed foods and increased psychological distress only occurred in individuals with a very high comparative intake of ultra-processed food.

A restricted cubic spline assessment was used to examine the relationship between ultra-processed food consumption and psychological distress. To this end, higher ultra-processed food intake was linked to an increased risk of increased psychological distress. Moreover, participants in the top quartile were significantly more likely to report psychological distress as compared to those in the first three quartiles.

Conclusions

The consumption of ultra-processed food was directly linked to increased psychological distress in subsequent follow-up visits. This association was solely observed in individuals who consumed a significant amount of ultra-processed food, specifically those in the highest quartile.

More research is needed to identify the negative aspects of ultra-processed food and develop effective nutrition and public health approaches to improve mental health.