Influence of eight ABCB1 polymorphisms on antidepressant response in a prospective cohort of treatment‐free Russian patients with moderate or severe depression: An explorative psychopharmacological study with naturalistic design

Background Many antidepressants are substrates of P‐glycoprotein, an efflux transporter in the blood‐brain‐barrier encoded by the ABCB1 gene. Genetic variations might influence the transport rate of antidepressants and hence their pharmacological effects. This study investigates the influence of eight polymorphisms in the ABCB1 gene on antidepressant treatment response. Method 152 patients were included from psychiatric departments of the Mental Health Research Institute in Tomsk. The difference in Hamilton‐Depression‐Rating‐Scale (HAMD‐17)‐scores between baseline and week two, week two and four, and baseline and week four was used to estimate timing of improvement of depression. Associations between the ABCB1 gene‐polymorphisms and reduction in HAMD‐17 score were assessed using independent t ‐test and multiple linear regression. Results Tricyclic antidepressants were associated with a higher reduction of HAMD‐17 score when compared to SSRIs. The SNP rs2235040 A‐allele had a significant positive influence on the ΔHAMD‐17 (0→2W) score but a significant negative influence on the ΔHAMD‐17 (2→4W) score. The rs4148739 G‐allele had a significant negative influence on the ΔHAMD‐17 (0→2W) score but a significant positive influence on the ΔHAMD‐17 (2→4W) score. The SNP rs2235015 T‐allele is significant negatively related to the ΔHAMD‐17 (2→4W) score. Conclusion ABCB1 Genetic variations appear to affect speed but not magnitude of antidepressant drug response.