It was an unwelcome shock for four people in Germany, when they suddenly had depression relapses. The condition had been kept at bay for four years by deep brain stimulation (DBS), a form of therapy whereby parts of their brains continuously receive electrical stimulation from deeply implanted electrodes.
All four experienced sudden and unexpected relapses, but recovered within around 12 hours when it was discovered that the batteries operating their implants had gone flat. The results counter suspicions that the benefits for DBS for depression are simply placebo effects.
One other person 鈥� who had been using DBS for two and a half years 鈥� also relapsed after deciding he didn鈥檛 need it anymore and deliberately switched the system off. He rapidly recovered after reactivating it.
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鈥淭hese cases deliver a very strong message against it being a placebo effect,鈥� says Thomas Schlaepfer, who has treated these and several other people at the Freiburg University Medical Center in Germany.
Although DBS has been used widely and with great success to treat thousands of people with Parkinson鈥檚 disease, doubts have surfaced about its effectiveness for severe depression. Two trials in 2015 delivered disappointing results, for example.
鈥淭here has been a large stigma to using DBS for depression, that it is largely a placebo effect,鈥� says Albert Fenoy, who also treats depression with DBS at the University of Texas in Houston. 鈥淪howing a quick relapse to depression after turning off the stimulation that previously improved their mood is great proof this is not due to a placebo effect.鈥�
Switching off
Schlaepfer says the treatment in the 2015 trials was too short-lived to have an impact. He hopes that his team鈥檚 results will dispel some of the doubt and revive efforts to trial DBS for depression.
His own team plans a follow-on trial in 60 people with depression who show sustained relief for at least six months while using DBS. In the following six months, their doctors will at some point 鈥� and with prior consent from all patients 鈥� switch off the device to see if they relapse. Only the doctors, not the patients or independent assessors of depressive state, will know it has been switched off to avoid any placebo effect.
Schlaepfer and Fenoy insert the electrodes in a part of the brain called the medial forebrain bundle, which plays a key role in motivation and reward. 鈥淎ll goal-directed behaviour is dictated by it,鈥� says Schlaepfer. With severe depression, people care less about pursuing rewards, 鈥渞estoring the reward system to normal is a very useful way to reverse that鈥�, he says.
