Association of poorer dietary quality and higher dietary inflammation with greater symptom severity in depressed individuals with appetite loss.

Background: Major depressive disorder (MDD) is the leading cause of years lived with disability; however, little is known about its etiology to inform treatment. For a subset of MDD patients, appetite change and/or bodily inflammation may play a role in exacerbating symptoms. The goal of this study is to examine whether, relative to healthy comparisons (HC), MDD individuals with increased versus decreased appetite symptoms show a differential relationship between diet quality and inflammation.

Methods: Unmedicated current MDD (n = 61) varying in appetite change (decrease (MDD-DE): n = 39; increase (MDD-IN): n = 22) and HC (n = 42) completed 24-hour dietary recall and state depression/anxiety measures. Healthy eating and dietary inflammatory indices were calculated from dietary reports. Blood samples measured five inflammation-related biomarkers. Analyses investigated between- and within-group differences in the Healthy Eating Index (HEI), the Dietary Inflammatory Index (DII), inflammation-related blood biomarkers, and symptom severity.

Results: While both MDD-DE and MDD-IN exhibited lower HEI scores than HC, only MDD-IN showed higher plasma interleukin-1 receptor antagonist (IL-1RA) and interleukin-6 (IL-6) levels than HC. In contrast, MDD-DE exhibited higher DII scores than MDD-IN and HC. Within MDD-DE, greater symptom severity was associated with lower HEI and higher DII.

Limitations: Modest sample sizes and the cross-sectional study design limited power to detect within-MDD effects.

Conclusions: Although MDD, regardless of appetite change, is linked to poorer dietary quality, depression severity was related to dietary characteristics only in subjects who reported appetite loss. Thus, increasing the quality of dietary intake could be a treatment target for some individuals with depression.