Depressed individuals have heightened C-reactive protein-to-albumin ratio

An analysis of data from the National Health and Nutrition Examination Survey found that individuals with depression tend to have a higher C-reactive protein-to-albumin ratio compared to those without depression. This finding remained consistent across different subgroups, including individuals with a history of metabolic diseases. The paper was published in the Journal of Affective Disorders.

Depression is a common mental health disorder characterized by persistent feelings of sadness, emptiness, or hopelessness that last for weeks or longer. An important symptom of depression is anhedonia — a loss of interest or pleasure in activities once enjoyed. People with depression may also experience changes in appetite and weight, either gaining or losing significantly. Sleep disturbances, such as insomnia or hypersomnia, are also common.

If left untreated, depression can severely impair daily functioning and increase the risk of self-harm or suicide. Unfortunately, current treatments are not effective for everyone, and many cases are classified as treatment-resistant. In addition, many individuals do not seek treatment, and among those who do, a large proportion fail to receive adequate care. Some estimates suggest that fewer than 20% of individuals with depression receive treatment that leads to full remission. This is why identifying new and more accurate methods for diagnosing depression remains a major focus of scientific research.

Study author Jing Lin and his colleagues sought to investigate whether the C-reactive protein-to-albumin ratio in blood might be associated with the risk of depression. C-reactive protein (CRP) is a substance produced by the liver in response to inflammation. Its levels rise quickly during infection or tissue injury. Albumin, also produced by the liver, is the most abundant protein in blood plasma. It helps maintain fluid balance and transports hormones, vitamins, and medications.

The C-reactive protein-to-albumin ratio (CAR) is calculated by dividing the CRP concentration by the albumin level in the blood. It reflects both acute inflammation (via CRP) and chronic or nutritional status (via albumin). Higher CAR values have been associated with worse outcomes in various health conditions, including infections, cancer, and cardiovascular disease.

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The authors analyzed data from the National Health and Nutrition Examination Survey (NHANES), a large, ongoing study designed to assess the health of a representative sample of non-institutionalized U.S. residents. For this analysis, data were drawn from 13,159 participants. The average age was 49 years, 49% were men, and 8% met criteria for depression.

Depression symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9), while CRP and albumin levels were measured from blood samples.

The researchers found that individuals with depression had significantly higher CAR values. This association was also observed across multiple subgroups, including those with pre-existing metabolic disorders.

“Our research findings demonstrated that an elevated CAR [C-reactive protein-to-albumin ratio] level was positively associated with depression. However, given the complexity of the underlying mechanisms and the need for broader generalizability, well-designed, large-scale prospective studies are imperative to further validate and solidify our current observations,” the study authors concluded.

The study results indicate that C-reactive protein-to-albumin ratio could potentially be used as a biomarker of depression. However, the design of the study does not allow any causal inferences to be derived from the results. Therefore, it remains unknown whether a high C-reactive protein-to-albumin ratio contributes to depressive symptoms or whether depression leads to increased C-reactive protein-to-albumin ratio. Other options for explaining this association also remain open.

The paper, “C-reactive protein-to-albumin ratio is associated with increased depression: An exploratory cross-sectional analysis,” was authored by Jing Lin, Xiang Yang, Zhiqiang Wu, Jiecong Lu, and Ming Zhang.