Everyone has days where they need to veg out with chips and soda, but eating certain ultra-processed foods, particularly artificially sweetened products, could lead to a higher risk for developing depression.

The findings come from a recent study published in the JAMA medical journal.

U.S.-based researchers monitored around 30,000 middle age female nurses over a four-year period.

There was a 50% increase in the risk of developing depression among participants who had nine portions of ultra-processed food (UPF) a day compared to those who had four portions or less.

The increase was especially high among those who drank a lot of artificially sweetened beverages.

“Although the mechanism associating UPF to depression is unknown, recent experimental data suggests that artificial sweeteners elicit purinergic transmission in the brain, which may be involved in the etiopathogenesis of depression,” the study’s authors wrote.

Participants who ate more processed food also had greater BMI, higher smoking rates, were less likely to exercise regularly were more likely to have diabetes and hypertension.

Ultra processed foods have five or more ingredients and typically have artificial colors and flavors. Examples of UPF’s include hot dogs, most breakfast cereals, frozen meals, fast food and soft drinks.

They are usually cheap and heavily advertised.