The results presented in the current paper indicate that SNPs located in genes encoding (i) POLG, a subunit of Pol γ involved in the replication, repair and degradation of mtDNA; (ii) ENDOG, an endonuclease with ability to induce apoptosis and autophagy as well as one of the candidates that is speculated to degrade damages mtDNA; and (iii) EXOG, an enzyme involved in mtBER are associated with the occurrence, onset, treatment and severity of depression (Figure 5). This evidence concerns the gene EXOG and depressive symptom measurement.