PTEN and treatment resistant depression: Regarding PTEN polymorphism, there was a statistically significant association between rs12569998 and TRD, with an overrepresentation of patients carrying TG genotype in the TRD group, which corresponds to an approximately four-fold increased risk to the development of TRD (OR: 4.231; 95% CI: (1.173–15.261); p = 0.020).