Electroconvulsive therapy (ECT) has been an effective yet controversial tool to treat severe depression for more than 70 years, and now Scottish researchers for the first time say they have discovered why the procedure often works the way it does.
ECT works by altering how different parts of the brain involved in depression communicate with each other. The University of Aberdeen and University of Dundee researchers, reporting in the journal Proceedings of the National Academy of Sciences (PNAS), said ECT involves anesthetizing patients with serious mood disorders, and then using an electric shock to induce a seizure. They said the method has been the most effective treatment available for seven decades.
ECT has the strongest supporting data among treatments for patients whose depression doesn´t respond to medication, according to the American Psychiatric Association. Between 10 and 20 percent of depressed patients received shock therapy, Paul Holtzheimer, an associate professor of psychiatry and surgery at Dartmouth Medical School, who was not involved in the new study, told Bloomberg‘s Elizabeth Lopatto.
“This gives us a much more powerful view of the brain,” he told Lopatto in a telephone interview. “If this study holds up, it tells us this is a network problem.”
In the Scottish study, nine patients scheduled for ECT had their brains scanned using functional MRI both before and after treatment. The MRI detects blood flow to specific regions of the brain. The team analyzed the brain´s connectivity using a new mathematical model.
“ECT is a controversial treatment, and one prominent criticism has been that it is not understood how it works and what it does to the brain,” said study leader Professor Ian Reid. “However we believe we´ve solved a 70-year-old therapeutic riddle because our study reveals that ECT affects the way different parts of the brain involved in depression connect with one another.”
Despite all the controversy surrounding the use of shock therapy, the procedure has probably helped 75 to 85 percent of patients recover from their symptoms, said Reid.
Reid said all nine patients in the study were diagnosed with severe clinical depression and were successfully treated with ECT — two sessions per week, an average of 8 total treatments. None of the patients in the study had responded to chemical antidepressants.
Using the new mathematical model to analyze brain connectivity, “we were able to find out to what extent more than 25,000 different brain areas ℠communicated´ with each other and how the brain´s internal communication patterns differed before and after ECT treatment in severely depressed patients,” said study co-author Professor Christian Schwarzbauer.
The researchers said their findings suggest a “hyper-connection” between the areas of the brain involved in emotional processing and mood change and the parts of the brain involved in thinking and concentrating. Our key finding is that if you compare the connections in the brain before and after ECT, ECT reduces the connection strength between these same areas – it reduces this hyperconnectivity.
And so, for the first time we can point to something that ECT does in the brain that makes sense in the context of what we think is wrong in people who are depressed.
“As far as we know no-one has extended that ℠connectivity´ idea about depression into an arena where you can show a treatment clearly treating depression, changing brain connectivity,” said Reid. “And the change that we see in the brain connections after ECT reflects the change that we see in the symptom profile of patients who generally see a big improvement.”
The team said they now hope to continue monitoring the patients to see if the depression and hyperconnectivity return.
“If we understand more about how ECT works, we will be in a better position to replace it with something less invasive and more acceptable,” said Reid. “At the moment only about 40 percent of people with depression get better with treatment from their GP.”
The findings may lead to new drug targets which match the effectiveness of ECR without an impact on memory, the researchers noted.
“These findings make a lot of sense,” Professor David Nutt, of Imperial College London, told BBC News. “Indeed, the disabling of connections between different areas of the brain is what I would have predicted from the depression literature.”
“This is why my research group is progressing psilocybin – which also disrupts this network, as we showed in PNAS recently – as a treatment for depression,” said Nutt, who was not involved in the Scottish study.
Schwarzbauer said their new method could be “applied to a wide range of other brain disorders such as schizophrenia, autism, or dementia, and may lead to a better understanding of the underlying disease mechanisms and the development of new diagnostic tools.”
He said more studies may lead to therapies that don´t have the side effects of ECT. Confusion, memory loss and physical pain such as muscle spasms are among the most common side effects of shock therapy. Also, a better understanding of how the brain region is affected in depression may enable doctors to better target patients who will benefit from treatment, he added.
“This is the start of a longer process,” Schwarzbauer said. “This is a very novel finding.”