High C-reactive protein levels are associated with depressive symptoms in schizophrenia

Background: Depressive symptoms are frequently associated with schizophrenia symptoms. C - Reactive protein (CRP), a marker of chronic inflammation, had been found elevated in patients with schizophrenia and in patients with depressive symptoms. However, the association between CRP level and depressive symptoms has been poorly investigated in patients with schizophrenia. The only study conducted found an association between high CRP levels and antidepressant consumption, but not with depressive symptoms investigated with the Calgary Depression Rating Scale for Schizophrenia (CDSS).

Objectives: The aim of this study was to evaluate CRP levels and depressive symptoms in patients with schizophrenia, and to determine whether high CRP levels are associated with depressive symptoms and/or antidepressant consumption, independently of potential confounding factors, especially tobacco-smoking and metabolic syndrome.

Methods: Three hundred and seven patients with schizophrenia were enrolled in this study (mean age = 35.74 years, 69.1% male gender). Depressive symptoms was investigated with the CDSS. Patients were classified in two groups: normal CRP level (≤ 3.0mg/L) and high CRP level (> 3.0mg/L). Current medication was recorded.

Results: 124 subjects (40.4%) were classified in the high CRP level group. After adjusting for confounding factors, these patients were found to have higher CDSS scores than those with normal CRP levels in multivariate analyses (p = 0.035, OR = 1.067, 95% CI = 1.004-1.132). No significant association between CRP levels and antidepressants consumption was found.

Limitations: The size sample is relatively small. The cut-off point for high cardiovascular risk was used to define the two groups. CRP was the sole marker of inflammation in this study and was collected at only one time point. The design of this study is cross-sectional and there are no conclusions about the directionality of the association between depression and inflammation in schizophrenia.

Conclusion: This study found an association between high rates of CRP levels and depressive symptoms in patients with schizophrenia, but no association with antidepressant consumption. Further studies are needed to investigate the impact of inflammation in schizophrenia.