It’s hard to tell which is the chicken and which is the egg here, which is always a problem with associations. Which is it: Are depressed people more likely to pass on cooking and order delivery? Or, is it that ordering delivery has a causal effect on depression? In this case, we might be able to assume the latter. ⠀⠀⠀⠀⠀⠀⠀⠀⠀
There have been studies establishing the causal role of inflammation on depression. For instance, pro-inflammatory proteins injected into healthy people is shown to cause depressive symptoms compared to placebo. In this meta-analysis of 11 studies (n= 101,950), a significant association between a pro-inflammatory diet and increased risk of depression was found - implying that an anti-inflammatory diet may be effective in preventing or reducing depression risk and symptoms.