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Updated: May 9, 2026
MRI-guided dmPFC-rTMS as a Treatment for Treatment-resistant Major Depressive Disorder
Published on: August 11, 2015
Structural and functional brain correlates of treatment-resistant depression: A systematic review of magnetic
Lauren E Carter1, Emily Lowery1, Mitul A Mehta2
1Centre for affective disorders, Kings College London, London, UK.
Abstract:
Despite depression being a leading cause of disability worldwide, traditional antidepressants are ineffective in around 30% of patients. This subset, labelled treatment-resistant (TR), further exhibit more severe depressive symptoms along with higher levels of suicidal thoughts and tendencies. While MRI studies reveal numerous brain alterations, findings are inconsistent due to varied methodologies. This systematic review synthesizes MRI-based evidence on TRD, comparing structural and functional changes with non-TR MDD. A search was conducted accross PubMed, Scopus, Web of Science, and EMBASE. Inclusion criteria required studies to compare TRD with another MDD subgroup such as treatment sensitive depression (TSD). A total of 27 studies with 22 TRD cohorts met inclusion criteria, comprising 14 studies with a TSD comparison group and 13 with non-TRD MDD comparisons. Regarding structural alterations in TRD, we highlight two major findings. The most robust is that of reduced hippocampal volume in TRD patients compared to non-TRD. The second is a reduction in white matter volume and integrity, although inconsistencies across studies make it unclear whether this is widespread or region-specific. Regarding FC, we highlighted regions of the frontal, temporal, and parietal lobes, along with the cerebellum to be altered in TRD. The DMN was also repeatedly implicated in TRD, with both hyper- and hypoconnectivity reported. This review suggests that, while treatment resistance in MDD likely presents with specific brain correlates, methodological variability prevents definitive conclusions. Standardised approaches, larger studies and accountability of various clinical factors are needed to better establish the underlying neurobiology of TRD.
Insights
Treatment-resistant depression (TRD) shows distinct brain changes, including reduced hippocampal volume and altered functional connectivity. More standardized research is needed to confirm these findings in major depressive disorder (MDD).
Area of Science:
- Neuroscience
- Psychiatry
- Medical Imaging
Background:
- Major depressive disorder (MDD) is a leading cause of global disability.
- Approximately 30% of MDD patients are treatment-resistant (TRD), experiencing more severe symptoms and higher suicide risk.
- Existing MRI studies on TRD brain alterations lack consistency due to methodological variations.
Purpose of the Study:
- To systematically review and synthesize MRI-based evidence on structural and functional brain changes in TRD.
- To compare these changes with those observed in non-treatment-resistant MDD (non-TRD) and treatment-sensitive depression (TSD).
Main Methods:
- Systematic literature search across PubMed, Scopus, Web of Science, and EMBASE.
- Inclusion criteria focused on studies comparing TRD cohorts with TSD or non-TRD MDD subgroups.
- Analysis of 27 studies involving 22 TRD cohorts.
Main Results:
- Consistent finding of reduced hippocampal volume in TRD patients compared to non-TRD.
- Evidence of reduced white matter volume and integrity in TRD, though specific regions are unclear.
- Altered functional connectivity (FC) in frontal, temporal, parietal lobes, cerebellum, and the default mode network (DMN) in TRD.
Conclusions:
- Treatment resistance in MDD appears associated with specific neurobiological correlates.
- Methodological inconsistencies across studies hinder definitive conclusions regarding TRD's underlying neurobiology.
- Standardized methodologies, larger sample sizes, and consideration of clinical factors are crucial for future TRD research.
