Effects of TIP treatment on brain network topology of frontolimbic circuit in first-episode, treatment-naïve major depressive disorder

The Low Resistance Thought Induction Psychotherapy (TIP) is a comprehensive psychological treatment which could improve the clinical symptoms of major depressive disorder (MDD). However, the neural mechanisms for TIP treating MDD still remain unclear. This study aimed to investigate the topology of intrinsic connectivity network and the therapeutic effects of TIP in MDD on these topological properties. Longitudinal study was conducted in 20 first-episode, treatment-naive MDD patients at baseline and after 6 weeks (12 sessions) of TIP treatment based on resting-state functional magnetic resonance image (rsfMRI) in conjunction with graph theoretical analysis. We constructed functional connectivity matrices and extracted the attribute features of the small-world networks in both MDD and age-, education level-, and gender-matched healthy controls (HCs). The global and local small-world network properties were explored and compared between MDD at baseline and HCs. The therapeutic effect of TIP was examined by comparing alterations in global and local network properties between MDD at baseline and after treatment. At baseline, MDD showed altered small-worldness and aberrant nodal properties in the frontolimbic circuit particularly in the orbital frontal gyrus, insula, precuneus and middle cingulate gyrus as compared with HCs. Following 6 weeks treatment, the abnormalities in the small-worldness and the nodal metrics were modulated, which were accompanied by a significant improvement in the clinical symptoms. Our findings contributed to the understanding of the abnormal topological patterns in the frontolimbic systems in MDD and implicated that these disruptions may be modified by TIP treatment.