Electrodes implanted deep inside the brain may provide considerable relief for just under half of people with the most severe depression for up to nine years, according to one of the longest-running clinical trials of its kind.
“They’ve taken the sickest of the sick and made almost half of them better, which is quite remarkable,” says at the University of Queensland, Australia, who wasn’t involved in the study.
The trial’s 25 participants had tried antidepressants, psychotherapies and electroconvulsive therapy for their severe depression, all without success.
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“They were at the point where they were sitting at home just trying to survive the day. They weren’t able to work, most did not have any social activities and many had had suicide attempts or were considering euthanasia,” says , who led the trial at Amsterdam UMC, a medical centre in the Netherlands. “voluntary and well-considered and [if the physician is satisfied] that his [or her] suffering is unbearable with no prospect of improvement”.
As part of the trial, the participants had tiny electrodes – each a few millimetres across – surgically implanted into a circuit of the brain that is implicated in severe depression.
Implanted between 2010 and 2014, the electrodes released impulses that it was hoped would improve connections within this circuit. “It’s like adding noise to a telephone cable – participants with severe depression have too much communication between certain brain areas, but adding this noise normalises this communication,” says Bergfeld.
The participants were monitored for six to nine years until a final check-up in 2019. At this point, 44 per cent were considered to have significantly benefited from the treatment, defined as their depression score reducing by 50 per cent or more from baseline. They also experienced a vast improvement in their quality of life.
“[They] were able to pick up new activities – hobbies, social activities and volunteering work – and some were even able to go back to work,” says Bergfeld.
Another 28 per cent partially benefited from the treatment, meaning their depression score reduced by 25 to 50 per cent. The remaining 28 per cent had zero or minimal improvements.
To check that those who improved hadn’t simply experienced a placebo effect, the trial included a 12-week period in which the electrodes were switched off for half the time, without the participants knowing when. Their depression scores then worsened, on average, suggesting the treatment effects are genuine.
It is unclear why some participants didn’t benefit from the deep brain stimulation, but one reason may have been that their electrodes weren’t hitting the right brain targets, says Mosley. “If they’re a millimetre or two in the wrong direction, they don’t work,” he says.
Several other small trials of deep brain stimulation for severe depression have found positive effects, but not all. The trials with positive results have tended to monitor participants for longer, says Mosley. “You can’t just flick a switch in the brain and change someone from depressed to not depressed – it takes time,” he says.
Bergfeld and his colleagues are now conducting a second trial to see if they can replicate their first study’s results. “If we manage to show an effect in more patients, then the ambition is to make this a standard treatment that’s more widely available to more patients,” he says.
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