A recent study investigating the relationship between diet and depression found that no significant dietary changes occur in senior adults at the onset of depression.
Depression is a medical condition that affects more than 15 million American adults and contributes substantially to the global burden of disease. Despite this, researchers and clinicians have failed to fully characterize the disorder and have very few effective strategies for its treatment. A better understanding of risk factors and the physiological basis of depression is critical for the development of novel prophylactic and therapeutic interventions. One factor thought to have an association with depression is diet; however, this relationship is not fully understood. As stated by the reverse causality hypothesis of depression and diet, it is unclear whether diet is a consequence or a cause of depression. Studies attempting to clarify the association have yielded contradictory findings, with results varying considerably depending on the sex and age of the cohort.
In a recent article, published in British Journal of Nutrition, Gougeon and colleagues explored the reverse causality hypothesis in older adults, to determine whether depression incidence is associated with a decline in dietary intake of nutrients. They conducted a 4-year observational study of 1,368 non-depressed senior men and women, with overall good health. During follow-up, there were 170 cases of depression, of which 12 were excluded due to a lack of dietary information. The incidence of depression was identified based on a Geriatric Depression Scale (GDS) score equal of greater than 11, or the use of a new antidepressant medication. Information on dietary intake was collected from three non-consecutive 24-hour dietary recalls. Sex and age matched controls were selected from the non-depressed participants to further conduct a case-control study.
The study demonstrated that mean energy, protein, and fibre intake were not significantly different between depression cases and controls. Moreover, their intake remained constant throughout the follow-up period. In contrast, saturated fat intake slightly increased over time in both depressed and non-depressed seniors, and thus was not attributed to the depressive status. B-vitamins, including vitamin B6, B12, and folate, were significantly lower in depressed seniors regardless of time point, compared to controls. It is possible that decline in B-vitamin levels precedes the onset of depression. However, the difference in B-vitamin intake was not exaggerated following the incidence of depression, and thus it is difficult to conclude whether a lack of B-vitamins contributes to depression onset and progression. Collectively, the study demonstrated that no major diet changes occurred acutely after depression incidence. Moving forward, longitudinal cohorts of longer duration are necessary to further investigate the extent of dietary decline following depression onset. Additionally, other dietary vitamins should be investigated to gain a more comprehensive understanding of the dietary changes that occur with depression. Studies should also focus on other social factors, like stressful life events and socioeconomic status, to determine whether they may contribute to depression onset and progression. In conclusion, depression is a complex disorder with many underlying confounding factors that all need to be thoroughly investigated.
Written By: Haisam Shah, BSc