Immune dysregulation contributes to the pathophysiology of depression and is a potential link between depression and comorbid medical conditions. DNA methylation is a dynamic transcriptional regulator of the immune system.

To study changes in DNA methylation of disease- and comorbidity-associated immune genes in patients with and without depression diagnoses from the German BiDirect Study.

We performed a cross-sectional (baseline, y0) and longitudinal (consecutive assessments at 3-year intervals, y0, y3, y6) differential methylation analyses of 382 immune-related genes associated with depression, obesity, diabetes and/or gout in 276 patients with depression and in 207 individuals without a lifetime depression diagnosis from the BiDirect Study. In addition, we applied unsupervised clustering to identify subgroups of individuals with depression based on longitudinal methylation patterns.

There were no significant methylation changes between individuals with depression and controls at baseline. Follow-up analyses used to assess the top (P < 0.05) 151 methylation probes longitudinally identified 42 CpG sites that showed time-dependent changes associated with depression, and defined 3 depression clusters with differential profiles of serum inflammation markers at baseline. The implicated genes corresponded in the majority to those associated with diabetes risk, and were enriched in processes relevant for haematopoiesis.

Our results suggest that immune dysregulation associated with DNA methylation profiles contributes to the pathophysiology of depression and is a plausible link to chronic medical conditions such as diabetes.

Previous studies suggested that exposure to traumatic events during childhood and adulthood and post-traumatic stress disorder (PTSD) are associated with a dysregulation of different neuroendocrine systems. However, the activity of the renin–angiotensin–aldosterone-system (RAAS) in relation to trauma/PTSD has been largely neglected.

Traumatization, PTSD, and plasma concentrations of renin and aldosterone were measured in 3092 individuals from the general population. Subgroups according to the status of traumatization (‘without trauma’; ‘trauma, without PTSD’, ‘PTSD’) were formed and compared regarding renin and aldosterone concentrations. Additionally, we calculated the associations between the number of traumata, renin, and aldosterone concentrations. Finally, associations of PTSD with renin/aldosterone levels were controlled for the number of traumata (‘trauma load’).

Levels of renin, but not aldosterone, were increased in traumatized persons without PTSD (p = 0.02) and, even stronger, with PTSD (p < 0.01). Moreover, we found a dose–response relation between the number of traumata and renin levels (β = 0.065; p < 0.001). Regression analyses showed PTSD as a significant predictor of renin (β = 0.38; p < 0.01). This effect was only slightly attenuated when controlled for trauma load (β = 0.32; p < 0.01).

Our results suggest that traumatization has lasting and cumulative effects on RAAS activity. Finding elevated renin levels in PTSD independent from trauma load supports the concept of PTSD as a disorder with specific neuroendocrine characteristics. Alternatively, elevated renin levels in traumatized persons may increase the risk for developing PTSD. Our findings contribute to explain the relationship between traumatic stress/PTSD and physical disorders.