Blood transcriptomic markers in patients with late-onset major depressive disorder

Search for the biomarkers of major depressive disorder (MDD) has facilitated from the genes expressed in the patient’s blood cells. Because the severity of depressive symptoms and characteristics in patients with MDD are differed by the age at onset of first depressive episode, the potential transcriptomic markers in blood cells may also be different by the age at onset of MDD. In this study, we searched the transcriptomic markers of late-onset (onset ages ≥ 50 years) MDD (LOD) from the expressed genes in blood cells, and identified state-dependent biomarkers in the patients. We assessed the expressed genes in blood cells by the microarray and found that the expression levels of 3,066 probes were state-dependently changed in the blood cells of patients with LOD. Elderly (age ≥50 years) outpatients and inpatients with MDD corresponding to a DSM-IV diagnosis of the melancholy type of MDD episodes were studied. The depressive state was measured using the Structured Interview Guide for the Hamilton Depression (SIGH-D) rating scale. Syndromal remission was defined as a stage in which a participant did not meet the diagnosis of a MINI major depressive episode for a period of 2 consecutive months and had a SIGH-D score of less than 8. Twelve healthy individuals were also recruited. Blood was obtained from the participants and analyzed using an Agilent SurePrint G3 Human GE 8×60K v2 Microarray (Design ID: 039494).