Do Repeated Episodes in Unipolar Depression Affect the DNA Damage, Repair Mechanisms and Cognitive Functions?

Abstract

Background: Memory impairments seen in depression have a significant role in daily functionality and work performance. In the pathogenesis of commonly seen and incapacitating diseases such as depression there is a need to clarify points that remain unknown. Aim: The aim of this study was to investigate the relationship between DNA damage, repair efficiency and cognitive functions in single episode and repeated episodes of depressive disorder. Methods: The study included 40 patients with a single episode of depression, 38 with repeated episodes and 40 healthy control subjects. DNA damage was examined using the comet assay method, and levels of OGG1, NEIL1, XRCC1 and APEX1 gene expression were measured using the real-time PCR method. The Verbal Memory Process Test was applied to all participants. The Hamilton Depression Rating Scale and Clinical Global Impression were also applied to the patient groups. Results: In the group with recurrent depression, it was observed that as the number of episodes increased and the duration of the disease lengthened, so the DNA damage increased. As DNA damage increased, so memory functions were observed to be impaired. DNA damage was associated with the decrease in the levels of DNA repair genes APEX1 and OGG1. The APEX 1 gene expression levels were determined to be reduced in the repeated depression group. Conclusions: The study results showed that as the number of depressive episodes increased, the effectiveness of DNA repair decreased and DNA damage increased, and the memory impairments seen in recurrent depression could be associated with DNA damage.