Eating ultra-processed food daily increases depression risk in older adults

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Mar 30 2025

A large-scale study of older Australians finds that diets high in ultra-processed food may quietly erode mental wellbeing—boosting depression risk and undermining quality of life, even without antidepressant use.

Study: The risk associated with ultra-processed food intake on depressive symptoms and mental health in older adults: a target trial emulation. Image Credit: Rimma Bondarenko / Shutterstock

In a recent study published in the journal BMC Medicine, researchers examined the impact of consuming ultra-processed food (UPF) on the mental health and symptoms of depression experienced by older adults. Their findings indicate that consuming four or more servings of UPFs each day is linked to a 10% higher risk of depressive symptoms and a modest but statistically significant decline in quality of life due to mental health, even among people who were not taking antidepressants at baseline.

Background

Mental disorders, especially depression, affect approximately 14% of older adults and are a growing concern. Often, depression in later life remains undiagnosed and can lead to several adverse health outcomes. Research shows that diet has a crucial role to play in promoting good physical and mental health, with poor diets contributing to chronic diseases, cognitive decline, and physical frailty.

One way to understand diet quality is through the Nova classification system, which categorizes foods based on their level of processing. Under this system, UPFs include industrially processed items that are higher in additives, fats, and sugars, such as ready-to-eat meals, sugary beverages, processed meats, packaged bread, diet soft drinks, and packaged snacks.

UPF consumption is increasing worldwide, with more than half of the overall energy intake derived from these foods in some high-income nations. Scientists have linked UPF intake to type 2 diabetes, cardiovascular diseases, and dementia. While UPFs have also been implicated in some mental health disorders, evidence of their relationship with depression remains inconsistent.

About the Study

In this study, researchers applied a target trial framework to investigate the impact of consuming UPFs on mental health and depressive symptoms among older adults. Since conducting randomized controlled trials (RCTs), which are considered the ‘gold standard’ in clinical research, is not always ethical due to challenges such as maintaining long-term dietary adherence or feasible in the context of mental health, target trial emulations offer a rigorous approach that allows researchers to draw causal inferences in observational studies.

The research team utilized data from a longitudinal study that included 11,192 older adults aged 70 and above in Australia, all of whom lived in community settings. All participants were free from major disabilities, dementia, and cardiovascular disease at the beginning of the study.

Outcome measures, namely general mental health and depressive symptoms assessed using the 10-item Center for Epidemiological Studies Depression (CES-D-10) scale, were measured in people who consumed four or more UPF servings a day and compared with those who consumed less than four. The CES-D-10 is a validated tool in older adults, capturing clinically relevant depressive symptoms.

Statistical approaches to mitigate the risk of biases in observational studies included the use of inverse probability treatment weights, followed by the application of marginal structural regression models. UPF intake was assessed using both servings per day and portion size/energy contribution in sensitivity analyses. A sensitivity analysis excluded people with depressive symptoms at baseline (defined as a CES-D-10 score ≥8) or those who used antidepressants at baseline.

Findings

Of the original study sample, 11,192 Australian adults with an average age of 74.9 were included in the study; slightly under 54% of participants were female. The average participant consumed 3.4 servings of UPFs per day, with males consuming slightly more than females (3.7 servings compared to 3.2 servings). Over 30% of the participants consumed four or more servings of UPFs each day.

More than 90% reported having good social support systems, 81.5% had multiple comorbidities, and nearly three-fourths consumed alcohol. After researchers used inverse probability treatment weighting, the high-UPF and low-UPF groups were well-balanced across other observed characteristics.

At baseline, 17.4% of individuals in the high UPF group had depressive symptoms, compared to 15.8% in the low UPF group. Over the next median of 5.8 years of follow-up observations, 41.8% developed symptoms of depression, with high UPF consumption increasing the risk of symptoms by 10%.

After excluding participants taking antidepressants at baseline, these results remained consistent, with high-UPF consumers showing an 11% increased risk. In subgroup analyses, the highest quartile of UPF intake showed a higher risk of depression; stronger associations were also noted for female participants, those with a higher body mass index, people without multimorbidities, and individuals with lower education, though the association was not statistically significant in males.

Higher UPF intake was also linked to lower mental health; on average, high UPF consumers had a 0.4-point lower mental health score (on the 100-point SF-12 Mental Component Score) than low UPF consumers, with a stronger effect observed in female participants.

Conclusions

These findings concur with previous studies that link UPF intake to poorer mental health outcomes, not only in older individuals but also among younger and middle-aged adults. The observed relationship may be due to UPFs disrupting the gut-brain axis and contributing to oxidative stress and inflammation, thereby affecting the body’s ability to regulate mood.

Despite the rigorous study design, the results could be affected by recall bias and measurement errors; the analysis also did not account for energy intake or dietary changes over time, and UPF intake was assessed using both servings per day and portion size/energy contribution.

However, the authors conducted an E-value analysis, finding that unmeasured confounders would need to have a risk ratio of ≥1.43 to fully explain the observed association, strengthening confidence in the results. While the 0.4-point decline in mental health scores was statistically significant, the authors caution that its clinical relevance—whether such a small change meaningfully impacts daily life—remains uncertain.

These findings warrant further investigations into improving mental health outcomes through dietary improvement interventions.