Australian research has for the first time established a link between diets high in ultra-processed foods and an increased risk of depression.

The recently published findings in the Journal of Affective Disorders show the risk of depression jumps markedly among people whose daily diet includes more than 30% ultra-processed food.

Dr. Melissa Lane, who completed the research as part of her Ph.D. studies at Deakin University’s Food and Mood Center, said the results provide further evidence of the wide-ranging harms of diets loaded with cheap, well-marketed but often nutrient poor convenience foods.

“While Australians eat a lot of ultra-processed foods, the link with depression has never been assessed in a group of Australians until now,” Dr. Lane said.

Ultra-processed foods are not limited to typical junk and fast foods. They also include mass-produced and highly refined products that might be considered relatively “neutral” or even “healthy” like diet soft drinks, some fruit juices and flavoured yogurt, margarine, packet preparations of foods like scrambled egg and mashed potato, and many ready-to-heat-and-eat pasta dishes.

Working with Dr. Priscila Machado from Deakin’s Institute for Physical Activity and Nutrition (IPAN) and Associate Professor Allison Hodge from the Cancer Council Victoria, Dr. Lane looked at associations between ultra-processed food consumption and depression in more than 23,000 Australians from the Melbourne Collaborative Cohort Study.

“Australians who ate the most ultra-processed food had about a 23% higher risk of depression compared to those who ate the least amount,” Dr. Lane said.

“Our study comprised people who were initially not taking any medication for depression and anxiety and followed them over 15 years,” Dr. Lane said.

“Even after accounting for factors like smoking and lower education, income and physical activity, which are linked to poor health outcomes, the findings show greater consumption of ultra-processed food is associated with a higher risk of depression.”

Dr. Lane said that while the study was not proof the ultra-processed food necessarily caused depression, it showed that eating more ultra-processed food was associated with an increased risk of depression.

“Depression is one of the most common mental disorders across the globe and it is a major health problem because it negatively affects daily living and wellbeing through lasting low energy, changes in appetite and sleep, loss of interest or pleasure, sadness, and sometimes thoughts of suicide,” Dr. Lane said.

“Identifying a critical level of consumption that may increase the risk of depression will help consumers, healthcare professionals and policymakers make more informed decisions around dietary choices, interventions and public health strategies.

“We hope this study will contribute to the promotion of mental wellbeing and guide efforts to prevent or reduce the prevalence, development and symptom severity of depression within the community.”