Biological Methods for Diagnosing Depressive Symptoms in Patients with Schizophrenia: A Narrative Review

Depressive symptoms in patients with schizophrenia lead to more frequent exacerbations of the underlying disease, worsen the prognosis, and increase the risk of suicide. Clinical practitioners continue to face challenges in diagnosing this disorder.

This study aims to analyze published material on biological markers of depressive symptoms in patients with schizophrenia.

The search of literature was conducted using the following electronic search engines (the total number of relevant papers found is also specified): ACCESSSS (n=150), Cochrane Library (n=48), PubMed (n=623), eLIBRARY (n=216), and Google Scholar (n=367). The final discussion included 67 papers consistent with the study aim and were published between January 1, 2018 and December 31, 2023.

Based on the available scaterred data, it appears that plasma biomarkers (e.g. C-reactive protein, metabolic parameters, hormones, enzymes, neurotrophic factors) are limited in specificity when it comes to diagnosing depressive symptoms in schizophrenia. Our analysis of the neuroimaging findings showed that depressive manifestations are associated with a decrease in the volume of the gray matter in the parietal, frontal, and temporal lobes (particularly in Broca's and Wernicke's areas) and in specific regions of the prefrontal cortex (including the medial right superior frontal, medial orbitofrontal, and superior and middle frontal gyri). It has been suggested that the SIRT1, OXT, CDKAL1, and APOE genes are involved in the development of depressive symptoms in patients with schizophrenia.

Understanding and identifying depressive symptoms in schizophrenia will improve the quality of care for patients with this disorder.