Data was obtained from the UK Biobank, a repository of data collected from tens of thousands of people across the United Kingdom.

It is important to remember that an observational finding like this is inherently not causational. One group of people weren’t asked to eat nuts while another was asked to not do so. Therefore, there is always the possibility that alternative explanations exist. A simple one could be: people that care more about their health tend to snack on healthier things like nuts instead of chips or sweets. And those people are less likely to be depressed.