Scientists hoped that brain stimulation would work in treating depression after noticing that epilepsy patients using Deep Brain Stimulation (DBS) therapy for seizures also saw improvements in emotional symptoms, such as anxiety.

For the treatment, the team placed temporary electrodes in several brain regions and delivered small pulses of stimulation, recording the clinical response.

They discovered that certain brain activity in the amygdala predicted a depressive episode, while stimulating the ventral striatum stopped it.

They then developed a device about the size of a matchbook that was implanted in Sarah’s skull with electrodes running to the two parts of the brain, to monitor amygdala activity then deliver a six second, one milliampere pulse to the ventral striatum.

Scientists found that Sarah’s brain activity triggered the device about 300 times a day, leading to 30 minutes of cumulative stimulation.

“When we turned this treatment on, our patient’s depression symptoms dissolved and in a remarkably short time she went into remission,” said first author on the study, Dr Katherine Scangos of the Weill Institute at the University of California San Francisco.

“Now, those thoughts still come up, but it’s just…poof…the cycle stops.

“What we are increasingly realising is that depression is caused by faulty neural circuits, but because every person is different it probably involves multiple neurocircuits.

“We found in Sarah the amygdala was a sub-circuit that was very specific to her depression.”

Commenting on the therapy, Jonathan Roiser, Professor of Neuroscience & Mental Health, University College London (UCL), said: “Although this kind of highly invasive surgical procedure would only ever be used in the most severe patients with intractable symptoms, it is an exciting step forward due to the bespoke nature of the stimulation.

“It is likely that if trialled in other patients, different recording and stimulation sites would be required, as the precise brain circuitry underlying symptoms probably varies between individuals.

“As there was only one patient and no control condition, it remains to be seen whether these promising results hold in clinical trials.”

The research was published in the journal Nature Medicine.