Nutritional psychiatry
Participants in the DNMC group experienced an increase from baseline in depression- and anxiety-like mood levels of 26.2% (95% confidence interval, 21-31.5; P = .001; P value using false discovery rate, .01; effect-size r, 0.78) and 16.1% (95% CI, 8.5-23.6; P = .005; PFDR, .001; effect-size r, 0.47), respectively.
By contrast, a similar increase did not take place in the DMI group for either depression- or anxiety-like mood levels (95% CI, –5.7% to 7.4%, P not significant and 95% CI, –3.1% to 9.9%, P not significant, respectively).
The researchers tested “whether increase mood vulnerability during simulated night work was associated with the degree of internal circadian misalignment” — defined as “change in the phase difference between the acrophase of circadian glucose rhythms and the bathyphase of circadian body temperature rhythms.”
They found that a larger degree of internal circadian misalignment was “robustly associated” with more depression-like (r, 0.77; P = .001) and anxiety-like (r, 0.67; P = .002) mood levels during simulated night work.
The findings imply that meal timing had “moderate to large effects in depression-like and anxiety-like mood levels during night work, and that such effects were associated with the degree of internal circadian misalignment,” the authors wrote.
The laboratory protocol of both groups was identical except for the timing of meals. The authors noted that the “relevance of diet on sleep, circadian rhythms, and mental health is receiving growing awareness with the emergence of a new field, nutritional psychiatry.”
People who experience depression “often report poor-quality diets with high carbohydrate intake,” and there is evidence that adherence to the Mediterranean diet is associated “with lower odds of depression, anxiety, and psychological distress.”
They cautioned that although these emerging studies suggest an association between dietary factors and mental health, “experimental studies in individuals with depression and/or anxiety/anxiety-related disorders are required to determine causality and direction of effects.”
They described meal timing as “an emerging aspect of nutrition, with increasing research interest because of its influence on physical health.” However, they noted, “the causal role of the timing of food intake on mental health remains to be tested.”
Novel findings
Commenting for this article, Kathleen Merikangas, PhD, distinguished investigator and chief, genetic epidemiology research branch, intramural research program, National Institute of Mental Health, Bethesda, Md., described the research as important with novel findings.
The research “employs the elegant, carefully controlled laboratory procedures that have unraveled the influence of light and other environmental cues on sleep and circadian rhythms over the past 2 decades,” said Dr. Merikangas, who was not involved with the study.
“One of the most significant contributions of this work is its demonstration of the importance of investigating circadian rhythms of multiple systems rather than solely focusing on sleep, eating, or emotional states that have often been studied in isolation,” she pointed out.
“Growing evidence from basic research highlights the interdependence of multiple human systems that should be built into interventions that tend to focus on one or two domains.”
She recommended that this work be replicated “in more diverse samples ... in both controlled and naturalistic settings...to test both the generalizability and mechanism of these intriguing findings.”
The study was funded by the National Institutes of Health. Individual investigators were funded by the Alexander Von Humboldt Foundation and the American Diabetes Association. Dr. Chellappa disclosed no relevant financial relationships. Dr. Merikangas disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.