How Does Electroconvulsive Therapy Affect the Brain?

What you need to know

• Electroconvulsive therapy (ECT) causes widespread increases in brain volume, particularly in regions involved in mood regulation
• These brain changes likely reflect a combination of increased plasticity and temporary disruption of neural circuits
• Understanding the brain effects of ECT may help explain how it relieves depression and guide improvements to the treatment

How ECT affects brain structure and function

Electroconvulsive therapy (ECT) is one of the most effective treatments for severe depression, but how exactly it works in the brain has long been a mystery. Brain imaging studies are now shedding light on the structural and functional changes that occur with ECT, potentially explaining its powerful antidepressant effects.

Widespread increases in brain volume

One of the most consistent findings from brain imaging studies is that ECT leads to increases in the volume of multiple brain regions. The hippocampus and amygdala, areas involved in memory and emotion, show some of the largest volume increases of 4-6%. But recent studies have found volume increases throughout most of the brain’s gray matter.

These volumetric changes appear quickly, sometimes after just two ECT sessions, and persist for weeks to months after treatment ends. The increases correlate with the number of ECT treatments received and the strength of the electrical current used.

Importantly, the volume changes seem to reflect actual growth of brain tissue rather than just fluid shifts. Brain imaging techniques that are sensitive to tissue microstructure suggest an increase in the number of neurons, synapses, or other cellular components.

Disruption followed by rewiring

While many studies have focused on ECT’s effects on brain plasticity and growth, there is also evidence that it temporarily disrupts brain function. Animal studies show that ECT can cause a short-term loss of synaptic connections, and human brain imaging reveals reduced connectivity between brain regions immediately after treatment.

The researchers propose a model where ECT first disrupts existing brain circuits, then enhances plasticity, allowing those circuits to rewire in healthier patterns. This may explain both ECT’s rapid effects and some of its side effects like confusion.

Changes in brain chemistry

In addition to structural changes, ECT also alters brain chemistry and metabolism. Studies have found changes in neurotransmitters like glutamate and GABA, as well as markers of neuronal health and metabolism. However, the results have been mixed, likely due to differences in timing and brain regions examined.

Linking brain changes to clinical effects

Despite the consistent finding of brain volume increases with ECT, studies have had difficulty linking these changes directly to improvement in depression symptoms. This may be because the volume increases reflect a mix of therapeutic and non-therapeutic effects.

More recent studies using machine learning techniques to analyze complex patterns of brain changes have shown some success in predicting which patients will respond to ECT. As methods improve, this could potentially help guide treatment decisions.

Conclusion and future directions

Brain imaging studies have revealed that ECT causes widespread structural and functional changes in the brain. The researchers propose a model where ECT first disrupts unhealthy brain circuits, then enhances plasticity to allow rewiring. This may explain both its therapeutic effects and side effects.

However, many questions remain about the exact biological mechanisms underlying these changes and how they relate to clinical improvement. Future studies using more advanced imaging techniques may help clarify these links and potentially lead to more targeted and effective treatments for depression.

• Conclusion 1: ECT causes widespread increases in brain volume, likely reflecting increased plasticity
• Conclusion 2: ECT may work through a combination of disrupting unhealthy circuits and enhancing rewiring
• Conclusion 3: More research is needed to fully understand how brain changes relate to clinical improvement