Individuals with mood disorders often exhibit chronic low-grade inflammation and immune system dysregulation. Some studies have highlighted immune dysfunction in these individuals, such as a higher frequency of autoimmune conditions and altered levels of certain pro-inflammatory cytokines. The presence of these factors can directly contribute to the development of depressive symptoms.
One protein of interest in this context is C-reactive protein (CRP), which plays a role in recognizing and eliminating pathogens and damaged cells by activating inflammatory mechanisms. CRP can have both pro-inflammatory and anti-inflammatory properties. Previous studies have shown higher levels of CRP in people with major depressive disorder (MDD), but we know less about how CRP levels differ in other mood disorders like bipolar and unipolar depression.
A recent study published in the Journal of Affective Disorders aimed to address this gap by evaluating CRP levels in individuals with unipolar and bipolar depression.
The study was conducted retrospectively, and patients diagnosed with a mood disorder were included in the analysis. Psychopathological rating scales were administered to assess general psychopathology, and blood samples were taken for further analysis.
To conduct the study, the researchers examined the records of patients who were consecutively hospitalized between December 1, 2021, and August 25, 2022. They only included patients who were 18 years or older and had a diagnosis of a current moderate-to-severe depressive episode within the context of major depressive disorder (MDD), bipolar disorder type I (BD-I), or bipolar disorder type II (BD-II), according to the DSM-5-TR criteria.
Out of a total of 313 patients who were screened during the period from December 2021 to August 2022, 113 patients provided written consent and were selected to participate in the study.
The researchers collected data from the patients’ electronic medical records, including socio-demographic information, family and personal psychiatry history, illness duration, previous and current medications, smoking habits, physical measurements, medical comorbidities, cardiovascular risk factors, and laboratory test results.
There were no significant differences in CRP levels based on sex, ethnicity, occupational status, marital status, smoking status, level of physical activity, presence of medical comorbidity, concomitant medical therapy, or family cardiovascular history.
Lower body mass index (BMI) was associated with lower levels of a specific type of CRP, while individuals with high blood pressure and abnormal blood fat levels exhibited higher levels of this CRP. These findings suggest a potential role for CRP in the development of conditions like high blood pressure, possibly through its impact on blood vessels.
The study also revealed a link between higher CRP levels and longer illness duration and earlier age of onset in mood disorders. Additionally, individuals with an eveningness-type chronotype had significantly higher CRP levels compared to morningness-type and intermediate-type individuals, indicating a consistent association between chronotype and CRP levels across different psychiatric conditions.
According to the researchers, the findings suggest that a neuroinflammatory approach could help group depressed patients into more homogeneous subgroups based on their inflammatory patterns. This approach could provide insights into the clinical course, treatment outcomes, and prognosis of these patients.
However, it’s important to consider some of the study limitations. The sample size was moderate, which means the results might not apply to all individuals with unipolar and bipolar depression. The study was also conducted at a single point in time, which makes it difficult to establish causal relationships or track changes over time. Further research is needed to conduct larger and longer-term studies that investigate how CRP levels may vary based on different factors such as mood levels.
The study, “Eveningness chronotype and depressive affective temperament associated with higher high-sensitivity C-reactive protein in unipolar and bipolar depression“, was authored by Laura Orsolini, Leonardo Ricci, Simone Pompili, Angelica Cicolini, and Umberto Volpe.