Epigenetic modifications, such as DNA methylation, contribute to the pathophysiology of major depressive disorder (MDD). This study aimed to identify novel MDD-associated epigenetic loci using DNA methylation profiles and explore the correlations between epigenetic loci and cortical thickness changes in patients with MDD.

A total of 350 patients with MDD and 161 healthy controls (HCs) were included in the epigenome-wide association studies (EWAS). We analyzed methylation, copy number alteration (CNA), and gene network profiles in the MDD group. A total of 234 patients with MDD and 135 HCs were included in neuroimaging methylation analysis. Pearson's partial correlation analysis was used to estimate the correlation between cortical thickness of brain regions and DNA methylation levels of the loci.

In total, 2018 differentially methylated probes (DMPs) and 351 differentially methylated regions (DMRs) were identified. DMP-related genes were enriched in two networks involved in the central nervous system. In neuroimaging analysis, patients with MDD showed cortical thinning in the prefrontal regions and cortical thickening in several occipital regions. Cortical thickness of the left ventrolateral prefrontal cortex (VLPFC, i.e. pars triangularis) was negatively correlated with eight DMPs associated with six genes (EML6, ZFP64, CLSTN3, KCNMA1, TAOK2, and NT5E).

Through combining DNA methylation and neuroimaging analyses, negative correlations were identified between the cortical thickness of the left VLPFC and DNA methylation levels of eight DMPs. Our findings could improve our understanding of the pathophysiology of MDD.

Early neurodevelopmental deviations, such as abnormal cortical folding patterns, are candidate biomarkers of major depressive disorder (MDD). We aimed to investigate the association of MDD with the local gyrification index (LGI) in each cortical region at the whole-brain level, and the association of the LGI with clinical characteristics of MDD.

We obtained T1-weighted images from 234 patients with MDD and 215 healthy controls (HCs). The LGI values from 66 cortical regions in the bilateral hemispheres were automatically calculated according to the Desikan–Killiany atlas. We compared the LGI values between the MDD and HC groups using analysis of covariance, including age, sex, and years of education as covariates. The association between the clinical characteristics and LGI values was investigated in the MDD group.

Compared with HCs, patients with MDD showed significantly decreased LGI values in the cortical regions, including the bilateral ventrolateral and dorsolateral prefrontal cortices, medial and lateral orbitofrontal cortices, insula, right rostral anterior cingulate cortex, and several temporal and parietal regions, with the largest effect size in the left pars triangularis (Cohen's f2 = 0.361; p = 1.78 × 10−13). Regarding the association of clinical characteristics with LGIs within the MDD group, recurrence and longer illness duration were associated with increased gyrification in several occipital and temporal regions, which showed no significant difference in LGIs between the MDD and HC groups.

These findings suggest that the LGI may be a relatively stable neuroimaging marker associated with MDD predisposition.

An aberrant neural connectivity has been known to be associated with bipolar disorder (BD). Local gyrification may reflect the early neural development of cortical connectivity and has been studied as a possible endophenotype of psychiatric disorders. This study aimed to investigate differences in the local gyrification index (LGI) in each cortical region between patients with BD and healthy controls (HCs).

LGI values, as measured using FreeSurfer software, were compared between 61 patients with BD and 183 HCs. The values were also compared between patients with BD type I and type II as a sub-group analysis. Furthermore, we evaluated whether there was a correlation between LGI values and illness duration or depressive symptom severity in patients with BD.

Patients with BD showed significant hypogyria in various cortical regions, including the left inferior frontal gyrus (pars opercularis), precentral gyrus, postcentral gyrus, superior temporal cortex, insula, right entorhinal cortex, and both transverse temporal cortices, compared to HCs after the Bonferroni correction (p < 0.05/66, 0.000758). LGI was not associated with clinical factors such as illness duration, depressive symptom severity, and lithium treatment. No significant differences in cortical gyrification according to the BD subtype were found.

BD appears to be characterized by a significant regionally localized hypogyria, in various cortical areas. This abnormality may be a structural and developmental endophenotype marking the risk for BD, and it might help to clarify the etiology of BD.

The hippocampus is not a uniform structure, but rather consists of multiple, functionally specialized subfields. Few studies have explored hippocampal subfield volume difference in the same sample of major depressive disorder (MDD) and bipolar disorder (BD) cases. We aimed to investigate the difference of hippocampal subfield volume between patents with MDD and BD and healthy controls (HCs).

A total of 102 MDD and 55 BD patients and 135 HCs were recruited and underwent T1-weighted image. Hippocampal subfield volume was calculated by automated segmentation and volumetric procedures developed by Iglesias et al. and implemented in FreeSurfer. Volume differences between the groups were analyzed using the analysis of covariance and controlling for age, sex, and total intracranial cavity volume.

Patients with MDD had significantly reduced volumes in the bilateral cornu ammonis 1 (CA1), CA4, the granule cell layer (GCL), molecular layer (ML), whole hippocampus, the left CA2/3, and right presubiclum and subiculum. Patients with BD had significantly reduced volumes in the right CA1, GCL, and the whole hippocampus as compared to HCs. No significant volume differences were observed between the MDD and BD groups. Illness duration was negatively correlated with volumes of the left CA1, CA4, ML, presubiculum, subiculum, and the whole hippocampus in patients with BD.

We observed hippocampal subfield volume reductions in both MDD and BD, a finding which more prominent in MDD. The inverse correlation between BD illness duration and hippocampal subfield volume may evidence the neuroprogressive nature of BD.

Noticeable demographic changes have taken place in South Korea, with the general marriage rate decreasing and the average first age at marriage and general divorce rate increasing. The shown trends have contributed to intergenerational discordance in the perception of familial values, which is important in addressing the psychological well-being of parents. This study aimed to investigate the association between the marital status of offspring aged 40 years and over and the depression levels of parents.

Data were from the Korean Longitudinal Study of Aging (KLoSA), 2006–2012. A total of 2,540 individuals with at least two offspring aged 40 years and over were included. Association between offspring marital status and parental depression scores, measured using the Center for Epidemiological Studies and Depression (CES-D 10) scale, was investigated using the generalized estimating equation (GEE) model. Subgroup analysis was performed based on offspring education level.

When parents with only married offspring were set as reference, parents with never married offspring (β: 0.27, p = 0.02), parents with separated offspring (β: 0.52, p = 0.03), and parents with never married offspring and separated offspring (β: 0.38, p < 0.001) showed increases in depression scores. In the subgroup analysis, these higher depression score effects were largely limited to parents with high school graduate offspring.

It is important to monitor the mental health status of parents with never married, separated, or both never married and separated offspring as this group may be comparatively vulnerable to depressive symptoms.

Suicide rates are high among elderly individuals experiencing socioeconomic insecurity. Socioeconomic security is of critical importance for elderly individuals and directly affects mental health, including suicidal behavior. Thus, we investigated the relationship between socioeconomic status and suicidal ideation in elderly individuals.

We conducted a cross-sectional study using data on 58,590 individuals 65 years of age or older from the Korean Community Health Survey 2013. Logistic regression analysis was used to identify relationships between socioeconomic factors (food insecurity, household income, and living arrangement) and suicidal ideation in the elderly population.

The study included 58,590 participants (24,246 males and 34,344 females). Of those, 2,847 males and 6,418 females experienced suicidal ideation. Participants with food insecure were more likely to experience suicidal ideation than were those who were food secure (males: OR = 1.60; 95% CI, 1.34–1.90; females: OR = 1.54; 95% CI, 1.38–1.72). We found a similar pattern among participants with a low household income and those living alone. Additionally, male and female subjects who were food insecure and living alone or food insecure and had a low household income showed a marked increase in suicidal ideation.

Our findings suggest that low socioeconomic status is associated with an increased risk of suicidal ideation among the elderly. Furthermore, intervention programs that address the prevalence of elderly suicide, particularly among those who are socioeconomically disadvantaged, are needed.