[padraigf]

Yes, the causation is poorly disentangled. He says:

"In our research, those who followed [a healthy, Mediterranean style diet] were 1.4 times more likely to have good night’s sleep and 35 percent less likely to have insomnia."

One naturally thinks "people who have healthy diets probably also make other healthy lifestyle choices, which may be the cause of the better sleep".

But this is never addressed.

[capitol_]

Or maybe: people who get enough rest have more energy that can be spent on eating healthy.