POLG and major depressive disorder: Although in the current paper POLG c.-1370T > A (rs1054875) did not affect the occurrence or severity of depression (Table 1, Table 4 and Table 5 and Figure 2C), analysis using the age of onset as continuous data revealed significant differences between the homozygotes, namely the A/A genotype carriers had their first episode significantly earlier in their lifespan than the T/T genotype carriers (Figure 1C).