Each fast food meal we eat in a week could increase our risk of developing depression by as much as 4%, according to a new study. Researchers from Iran also found that eating more than two fast food meals per week could increase the risk by almost a quarter. They wanted to look at the effect of eating fast food on both obesity and depression. Previous studies have found that eating a lot of heavily processed foods could lead to depression. The research team thought that eating a lot of fast food was likely to cause obesity and that this could lead to depression. However, they found obesity was not as much of an important factor as they thought it would be, and perhaps it was fast food consumption — and not obesity — that increased the risk of depression. The researchers looked at data from more than 31,000 people in the US, taken between 2008 and 2018. The participants were asked how many fast food meals they ate in a typical week, and they answered a survey that asked them about symptoms of depression. During the study period, 11% of women and 7% of men showed signs of depression, although those with higher levels of education were less likely to be depressed. Those who ate more than two fast food meals a week had a 24% higher risk of depression compared to those who ate fewer than two fast food meals per week. However, the researchers say they can't prove that the cause of the participants' depression was eating fast food.