Healthy and Unhealthy Dietary Patterns Are Related to Depression: A Case-Control Study

Major depressive disorder is the leading cause of disability around the world. The relationship between depression and dietary patterns has been reported in a few studies but with controversial results. This study aimed to investigate this relationship in an Iranian population.

In our study, 330 depressed patients (cases) and healthy people (controls) (1:2) were individually matched according to age, sex and area of residence. New cases of depression were recruited from two psychiatric clinics in Tehran. Interviewers went to each patient's residential area, and invited qualified individuals to participate in the study as controls. Food intake over the past year was collected using a validated semi quantitative food frequency questionnaire. Dietary patterns were determined by the principal components method. Binary logistic regression was used to test the effect of dietary patterns on depression.

We identified two major dietary patterns by using factor analysis: the healthy and unhealthy dietary patterns. We categorized the scores of these patterns to quartiles. After adjusting for non-depression drug use, job, marital status, children number, and body mass index, the relations of depression and quartiles of two dietary patterns are significant (p=0.04 & p=0.01, respectively). Compared with participants in the lowest quartile, those in the highest quartile had significantly lower odds ratio (OR) for depression in healthy dietary pattern, and higher OR for depression in unhealthy dietary pattern.

This study indicates that healthy and unhealthy dietary patterns may be associated with the risk of depression. The results can be used for developing interventions that aim to promote healthy eating for the prevention of depression.