Whole blood mitochondrial DNA copy number in depressed patients with and without a history of adverse childhood experiences: the role of blood cell composition

Adverse childhood experiences (ACE) are a significant risk factor for developing major depressive disorder (MDD) later in life, with mitochondria, key sensors of biological stress signals, emerging as a potential underlying mechanism. In the present study, we investigated the effects of ACE and MDD on whole blood mitochondrial DNA copy number (mtDNAcn), a proposed biomarker of mitochondrial health. In our analyses, we accounted for the platelet-to-leukocyte ratio, recognised as a source of variation in mtDNAcn measurements. Whole blood mtDNAcn was measured by qPCR in n = 21 healthy participants without ACE, n = 25 MDD patients without ACE, n = 22 healthy participants with ACE, n = 23 patients with MDD and ACE. None of the participants was taking psychotropic medication. We observed a significant effect of ACE on whole blood mtDNAcn, while no effect of MDD or ACE and MDD interaction was seen. After adjustment for the platelet-to-leukocyte ratio, the effect of ACE on mtDNAcn was no longer significant. Our findings do not support an association between ACE or MDD and whole blood mtDNAcn. Considering blood cell composition may enhance the understanding of whole blood mtDNAcn findings in trauma‑ and MDD‑related research.