Understanding the Variability of Associations Between Higher Ultra-Processed Food Consumption and Self-Reported Depression Severity: A Systematic Review of Epidemiological Studies

Background/Objectives: Coinciding with an increasing trend of ultra-processed food (UPF) consumption, nations are experiencing a surge of diet-related chronic diseases such as diabetes and other metabolic conditions. While many studies have found positive associations of UPF consumption with physical health outcomes, few studies have examined the effects of UPF consumption on mental health conditions. Therefore, the purpose of this systematic review is to understand the variability of associations between higher UPF consumption and depression severity across research studies with adult populations. Methods: Using PsychINFO, CINAHL Ultimate and Web of Science databases, we conducted a systematic review of recent observational studies examining the association of UPF consumption with self-reported depression in adult populations. To assess the quality of each study, Strengthening the Reporting of Observational Studies in Epidemiology—Modified (STROBE-M) checklist was used to assess risk of bias in each of the included studies. Results: Of the 530 records retrieved, 13 studies with a total of 264,519 participants met all eligibility criteria and were included in this review. All 13 studies reported a positive association between higher UPF consumption and depression severity, ranging from 1.15–2.04 (Hazard, Odds, and Relative Risk ratios). Some of the studies likely experienced selection bias due to loss of participants to follow-up. Conclusions: In adult populations, observational studies indicated a low to moderately increased risk of self-reported depression among those with diets that include higher amounts of ultra-processed foods.