Evidence from five waves of a national survey of Canadians

The association between fruit and vegetable consumption and mental health disorders:
(McMartin et al. 2013¹)

Study: repeated cross-sectional national study
Sample: Canadian Community Health Survey (CCHS) between 2000 until 2009 (n=296,121 aged 12 years or older).
Outcome: a major depressive episode over the previous 12 months
Exposure of interest: fruit and vegetable intake

The relationship between fruit and vegetable consumption and mental health was examined using statistical models (logistic regression), controlling for other characteristics such as gender, age, household income, education, physical activity level and chronic illness. 

Odds ratio of 0.73 (with its 95% Confidence Interval of 0.71-0.75) represents the across years pooled estimate for the association between fruit and vegetable consumption and depression. Thus, greater fruit and vegetable consumption was associated with a reduction in odds of depression relative to those consuming the least amount of fruits and vegetables.