I came across a randomized controlled trial in JAMA Internal Medicine from July this year that tries to examine the relationship between cognition, Mediterranean diet and nuts (available here). It had some positive results but overall it seemed the p values were not that impressive given the multiple testing. However, it reminded me of a more interesting study PREDIMED from a couple of years ago (here) that looked at the relationship between diebetes risk, depression, Mediterranean diet and nuts. Those taking Mediterranean diet and nuts had lower risk of depression during follow up.