In this nationally representative cross-sectional study, we evaluated the relationship between the PNI and depression. The pivotal discovery of this research is that a low level of PNI was associated with higher odds of having depression in the US adult population. This association persists even after conducting various stratified and sensitivity analyses. To the best of our knowledge, this study is the inaugural investigation into the correlation between PNI and depression within a general population context.
The intricate relationship between depression and the PNI warrants further exploration, and multiple plausible explanations may shed light on this association. Firstly, individuals experiencing depression often exhibit compromised nutritional status18, which could be reflected in a lower PNI10. Several studies have highlighted the connection between depressive symptoms and poor nutritional intake18–21, emphasizing the role of nutritional deficiencies in mental health. Notably, a study encompassing a substantial cohort in the NHANES database demonstrated that a lower PNI was associated with a higher risk of depression. This finding echoes previous research that links depression to malnutrition and supports the potential role of PNI as an indicator in assessing mental health status.
Secondly, the relationship between PNI and depression might be mutual. While a lower PNI signifies nutritional insufficiency, it also serves as a marker for adverse health conditions, including chronic diseases, immune dysfunction, and inflammation22–25. These health complications associated with a lower PNI could contribute to the onset or exacerbation of depressive symptoms26–29. In our study, individuals with higher depression rates exhibited lower PNIs, indicating a potential interplay between nutritional status and mental health.
Moreover, inflammatory markers and oxidative stress, both influenced by nutritional status30,31, are recognized contributors to the pathophysiology of depression32. Studies have revealed that a diminished PNI correlates with elevated levels of inflammatory markers33,34. Furthermore, oxidative stress, known for inducing albumin denaturation, triggers a rapid decline in serum albumin levels35,36, thereby contributing to a reduction in PNI. These physiological imbalances may implicate a biological link between lower PNI and an increased susceptibility to depression, underscoring the importance of considering nutritional status in mental health management.
Our findings contribute significantly to understanding the intersection of nutritional status and depression, particularly within the general population. Individuals with compromised nutritional status often face metabolic irregularities and immune system dysfunctions, both of which can impact mental well-being37,38. Notably, maintaining a healthy PNI might serve as a preventive measure against the development or progression of depression. Additionally, considering the potential impact of nutritional status on mental health, interventions aimed at improving PNI through dietary modifications or nutritional supplementation might be beneficial in alleviating depressive symptoms. Previous studies have highlighted the impact of specific nutrients on mental health outcomes39,40, emphasizing the role of a well-balanced diet in supporting overall well-being, including mental health41,42.
However, our study has several limitations that necessitate consideration. Firstly, its cross-sectional design precludes establishing causality between PNI and depression. Furthermore, the findings may not be universally applicable across different ethnic groups or regions, as the study primarily focuses on data from the United States. Additionally, the reliance on self-reported depressive symptoms for a one-time assessment may not fully capture the spectrum of depression severity and longitudinal fluctuations. Moreover, the absence of detailed medication data and its potential influence on both depression and nutritional status poses a limitation in our analysis.
In conclusion, our study underscores the association between Prognostic Nutritional Index and depression within the NHANES cohort. While highlighting the intricate interplay between nutritional status and mental health, it suggests avenues for further research exploring the role of nutritional interventions in managing depression. Despite limitations, this investigation lays a foundation for future multi-center cohort studies aiming to elucidate the nuanced relationship between PNI and depression and its potential implications for mental health interventions.