Background

The goal of this systematic review was to determine whether dietary patterns are associated with risk of depression. Dietary patterns were defined as the quantities, proportions, variety or combination of different foods, drinks and nutrients in diets; and the frequency with which they are habitually consumed.

Conclusion statement

Limited evidence suggests that dietary patterns emphasizing seafood, vegetables, fruits, nuts and legumes are associated with lower risk of depression in men and non-perinatal women. However, the body of evidence is primarily composed of observational studies and employs a range of methodology in study design, definition and measurement of dietary patterns and ascertainment of depression or depressive signs and symptoms. Studies on dietary patterns in other populations such as women in the postpartum period, children and adolescents, as well as those in various ethnic and cultural groups, are too limited to draw conclusions.

2015 DGAC Grade:

• Adults: Limited
• Postpartum women, children and adolescents: Not assignable

Methods

Literature searches were conducted using PubMed, Embase, Navigator (BIOSIS, CAB Abstracts and Food Science and Technology Abstracts) and Cochrane databases to identify studies that evaluated the association between dietary patterns and risk of cognitive impairment, dementia and Alzheimer’s disease. Studies that met the following criteria were included in the review: randomized controlled trials (RCTs), non-randomized controlled trials, or prospective cohort studies; human subjects aged two years and older who were healthy or at elevated chronic disease risk; subjects from countries with high or very high human development (2012 Human Development Index); and published in English in peer-reviewed journals. The date range was January 1980 to January 2014. The intervention or exposure was adherence to a dietary pattern (e.g., a priori patterns, data-driven patterns, reduced rank regression (RRR) or patterns derived from other methods and a description of the dietary pattern(s) (i.e., foods and beverages) consumed by subjects was provided. The outcome was incidence of depression.

Data from each included article were extracted, and risk of bias was assessed. The evidence was qualitatively synthesized, a conclusion statement was developed and the strength of the evidence (grade) was assessed using preestablished criteria including evaluation of the quality/risk of bias, quantity, consistency, magnitude of effect and generalizability of available evidence.

Findings

• This systematic review includes 19 articles (17 from prospective cohort studies, and Systematic Reviews of the Dietary Patterns, Food and Nutrients Subcommittee, 2015 DGAC 105 Archived from www.NEL.gov on March 21, 2017 two using data from RCTs) published since 1980 (all of which were published since 2008) that assessed the relationship between dietary patterns and depression
• The articles used several different methods to assess dietary patterns. Two studies tested the effects of dietary patterns as part of an RCT, six articles used indices and scores to assess dietary patterns, 10 articles used data-driven methods and one used RRR. Despite methodological and outcome heterogeneity in this body of evidence, some protective dietary patterns emerged:
  • Patterns emphasizing seafood, vegetables, fruits and nuts were generally associated with reduced risk of depression
  • Patterns emphasizing red and processed meats and refined sugar were generally associated with increased risk of depression.

Limitations

The ability to draw strong conclusions was limited by the following issues:

• There was considerable variability in how the outcome of depression was assessed, with some studies using various depression scales, some using physician diagnosis and hospital discharge records and others using proxies such as use of depression medication
• Although most studies make extensive efforts to include participants across a wide range of race/ethnic groups and across the socioeconomic continuum, there still may be some subgroups for which the association between dietary patterns and depression risk cannot be reliably assessed; therefore, conclusions cannot be drawn for them. Research is needed to determine whether dietary patterns are associated with risk of depression in particularly vulnerable subgroups, specifically children, adolescents, young adults, and women during the postpartum period
• Additional limitations within this body of evidence make it difficult to draw stronger conclusions, including assessment of dietary patterns and depression outcomes at a single point in time, potential for residual confounding despite adjustment for a number of factors and few studies conducted in US-based populations.