Electroconvulsive therapy alleviates depression symptoms by increasing aperiodic activity

Electroconvulsive therapy (ECT), formerly known as electroshock therapy, uses controlled doses of electricity to induce a brief seizure in the brain. Although ECT is highly effective for certain mental illnesses, particularly depression, the reasons for its effectiveness have long puzzled the fields of psychiatry and neuroscience.

Now, researchers at the University of California San Diego may have an answer. In two new studies published on November 16, 2023 Translational psychiatryThey propose a new hypothesis that ECT alleviates symptoms of depression by increasing aperiodic activity, a type of electrical activity in the brain that does not follow a consistent pattern and is generally considered background noise in the brain.

“We are solving a puzzle that has baffled scientists and doctors since electroconvulsive therapy was first developed nearly a century ago,” said first author Sidney Smith, a PhD candidate in the Voytech Lab at UC San Diego. “On top of that, we’re helping to demystify one of the most effective, yet stigmatized treatments for major depression.”

Electroconvulsive therapy has an excellent track record, but a bad reputation. The therapy is effective in up to 80% of patients who receive treatment, mostly for depression but occasionally for bipolar disorder or schizophrenia. However, despite this high success rate, electroconvulsive therapy is often associated with frightening images of people receiving painful, high voltage shocks.

“Many people are surprised to learn that we still use electroconvulsive therapy, but modern methods use highly controlled doses of electricity and are done under anesthesia,” says Smith. “It’s not really what you see in the movies or on television.”

Although generally safe and effective, ECT has drawbacks, including temporary confusion and cognitive impairment. It also requires multiple outpatient visits, which can present a barrier to some people who might otherwise benefit from treatment.

One reason ECT is not more popular is that for many people, it is easier and more convenient to just take one pill. However, electroconvulsive therapy can be lifesaving in people for whom medication does not work. Understanding how it works will help us discover ways to increase benefits while minimizing side effects.”

Bradley Voytek, Ph.D., Senior Writer, Professor of Cognitive Science at UC San Diego

Researchers used electroencephalography (EEG) scans to study brain activity in patients receiving ECT therapy for depression. They also looked at another similar treatment called magnetic seizure therapy, which induces seizures with magnets instead of electrodes. Both therapies increased the level of aperiodic activity in the brains of patients after treatment.

“Aperiodic activity is like background noise in the brain, and for years scientists treated it that way and didn’t pay much attention to it,” says Smith. “However, we now see that this activity actually plays an important role in the brain, and we think electroconvulsive therapy can help restore this function in depressed people.”

One function of aperiodic activity in the brain is to help control how neurons turn on and off. Our neurons are constantly going through cycles of excitation and inhibition that correspond to different emotional states. Aperiodic activity helps increase inhibitory activity in the brain, effectively lowering it.

“What we routinely see on EEG scans of people receiving electroconvulsive or magnetic seizure therapy is a slow pattern of electrical activity in the brain,” Smith said. “This pattern went unexplained for many years, but accounting for the inhibitory effects of aperiodic activity helps explain it. It also suggests that these two types of therapy are causing similar effects in the brain.”

While these findings establish a link between aperiodic activity and ECT benefits, the researchers emphasize the need for further investigation to harness these insights into clinical applications. They are currently exploring the possibility of using aperiodic activity as a metric of treatment effectiveness in other depression treatments, such as medication.

“At the end of the day, the most important thing to patients and doctors is that the treatment works, which in the case of ECT, it does,” says Voytek. “However, it is our job as scientists to find out what is actually happening in the brain during these treatments, and continuing to answer these questions will help us find ways to make these treatments more effective while minimizing the negative effects.”