What Goes Up, Also Goes Down: What happens to the brain after ECT?

In the treatment of severe depression, Electroconvulsive Therapy (ECT) has long been an effective method. While the initial effects of ECT on the brain have been widely studied, new research highlights the fascinating pattern of gray matter volume (GMV) changes after treatment. My recent article in Brain Stimulation, Characterization of Gray Matter Volume Changes from One Week to Six Months After Termination of Electroconvulsive Therapy in Depressed Patients, examines this phenomenon, revealing that what goes up, also goes down.

The Initial Increase

ECT's immediate impact on the brain is significant. Within a week after treatment, there is a notable increase in GMV in various brain regions. This increase is linked to neuroplasticity—the brain's ability to reorganize by forming new neural connections. This rise in GMV post-ECT is consistent with earlier findings and highlights the treatment's initial effectiveness in altering brain structure. Important note; it is not clear whether the structural neuroplasticity is an essential element of the antidepressant effect of ECT.

The Decrease Over Time

However, the story doesn't end there. Our study, using data from the Global ECT-MRI Research Collaboration (GEMRIC), which is the largest dataset of its kind, observed that this increase in GMV is followed by a gradual decrease. Over one to six months after ECT, GMV in most brain regions begins to revert to baseline levels. This pattern was consistently observed in 63 out of the 84 regions of interest studied. Meaning, when GMV increased during ECT, it decreased when ECT was terminated in the majority of brain regions.

Lasting Changes in Key Areas

Interestingly, not all regions returned to their original state. Specific areas related to cognitive and emotional regulation, such as the amygdala and hippocampus, retained higher GMV even six months post-treatment. This lasting increase suggests that these regions might undergo longer-term structural changes, which could help understand the cognitive side effects often linked to ECT.

Clinical Implications and Future Directions

One of the most intriguing findings of our study was the lack of a consistent relationship between GMV changes and clinical depression outcomes. This indicates that while ECT causes significant neurobiological changes, these changes do not directly correlate with the clinical improvements seen in patients. This highlights the complexity of depression and the multifaceted nature of its treatment.

The Role of Neuroplasticity

The temporary nature of GMV changes post-ECT could be due to the brain's inherent plasticity. After the initial increase in GMV, homeostatic mechanisms may stabilize the synaptic network, contributing to the observed decrease. This fits with the broader principle of neural plasticity, where an initial overproduction of connections is followed by a period of pruning and stabilization.

Conclusion

Our study provides insights into the dynamic nature of brain changes following ECT, highlighting a pattern of increase followed by a decrease in GMV. These findings deepen our understanding of how ECT impacts the brain and underscore the importance of considering both short-term and long-term effects in clinical practice. As we continue to explore the complexities of ECT and its effects on the brain, it becomes increasingly clear that what goes up, must indeed come down, albeit in a nuanced and region-specific manner.

The changes in gray matter volume post-ECT demonstrate the brain's remarkable ability to adapt and reorganize. By further studying these changes, we can better understand the underlying mechanisms of ECT and improve its application in treating severe depression.

Special thanks to Louise Emsell, Leif Oltedal and the GEMRIC consortium for their data and help regarding this research article.

GEMRIC diner at SOBP 2023, San Diego, USA

Reference:

Laroy et al. (2024). Characterization of gray matter volume changes from one week to 6 months after termination of electroconvulsive therapy in depressed patients. Brain Stimulation 17(4):876-886. doi: 10.1016/j.brs.2024.07.015