New studies explain how electric shock therapy treats depression

Two new studies may have discovered the mechanism by which electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) are effective in treating depression.

ECT, which induces a brief seizure in the brain using controlled doses of electricity, was used throughout much of the twentieth century to treat mental illness, including severe depression. Although it developed a reputation as a severe and even cruel therapy, it is still used in cases of severe depression that are resistant to other forms of treatment, and has an effectiveness rate of 80%.

What scientists don’t know, however, is why ECT works. Researchers at the University of California San Diego have carried out two pieces of research, both published in the journal Translational Psychiatry, that suggest a mechanism by which ECT alleviates depression.

“A lot of people are surprised to learn that we still use electroconvulsive therapy, but the modern procedure uses highly controlled dosages of electricity and is done under anaesthesia,” said Sydney Smith, lead and corresponding author of both studies. “It really doesn’t look like what you see in movies or [on] television.”

In the first study, the researchers used electroencephalography (EEG) to study the brain activity of patients who received ECT for depression. In the second, they looked at a similar form of treatment called magnetic seizure therapy (MST), which induces a seizure using magnets instead of electrodes. MST was developed as an alternative to ECT because it has fewer side effects.

Aperiodic activity – the brain’s background noise

The researchers found that both therapies produced an increase in aperiodic activity in the patient’s brains. “Aperiodic activity” is, according to Smith, “the brain’s background noise.” For years, she said, scientists didn’t pay much attention to it.

She added: “However, we’re now seeing that this activity actually has an important role in the brain, and we think electroconvulsive therapy helps restore this function in people with depression.”

The brain’s neurons constantly cycle through periods of excitation and inhibition, and these cycles correspond to different mental states. Aperiodic activity helps to boost inhibitory activity in the brain, effectively slowing it down.”

“Something we see regularly in the EEG scans of people who receive electroconvulsive or magnetic seizure therapy is a slowing pattern in the brain’s electrical activity,” Smith said. “This pattern has gone unexplained for many years, but accounting for the inhibitory effects of aperiodic activity helps explain it. It also suggests that these two forms of therapy are causing similar effects in the brain.”

The researchers said their findings suggest that ECT and MST reduce depressive symptoms by restoring healthy levels of inhibition in the brain. While the studies establish a link between aperiodic activity and these treatments, more research needs to be done to make use of the findings in clinical applications.

They are currently looking at the possibility of using aperiodic activity as a metric of treatment effectiveness in other depression treatments, including medication.

“At the end of the day, what’s most important to patients and to doctors is that the treatment works, which in the case of ECT, it does,” said Bradley Voytek, a co-author on both studies. “However, it’s our job as scientists to dig into what’s really going on in the brain during these treatments, and continuing to answer those questions will help us find ways to make these treatments even more effective while reducing negative effects.”