Deep brain stimulation helped half of patients with severe persistent depression

Severe depression remains one of the most common and difficult mental health problems to treat. Antidepressants and psychotherapy do not help everyone, and about a third of patients experience persistent resistance when even combined treatment does not work. It is for such cases that scientists are looking for new approaches, and DBS is considered as one of the promising alternatives.

The study involved 26 patients from Ruijin Hospital (Shanghai) who had been suffering from severe depression for years, immune to conventional methods. The electrodes were placed in two areas of the brain at once.

• The first is the area of BNST associated with stress, anxiety, and reaction to prolonged emotional stress.
• The second is the nucleus accumbens, a key center of pleasure, motivation, and emotional reinforcement.
  Both areas have long been considered important in the mechanisms of depression, and scientists wanted to understand whether the effect would increase if they were affected simultaneously.

The results were impressive: 13 out of 26 people had significantly reduced symptoms of depression and anxiety. Nine participants achieved remission — that is, almost complete disappearance of the manifestations of the disease. Patients reported improved well-being, decreased anxiety, and improved quality of life.

A particularly valuable part of the study was that the scientists were able to identify an objective feature by which it is possible to determine in advance who the treatment will help the most.

This sign turned out to be theta activity, a type of electrical activity in the brain in the range of 4-8 Hz. The electrodes in the BNST and the EEG data showed that the higher the theta rhythms in this zone, the more severe the depression and anxiety.

People with lower theta activity before surgery, as it turned out, responded to treatment the best of all. Moreover, synchrony between the BNST and the prefrontal cortex, an area responsible for emotion control, also played an important role. The better these two zones communicated with each other, the more noticeable the reaction to DBS was.

Interestingly, as the treatment progressed, theta rhythms decreased – and this decrease exactly coincided with clinical improvements. This opens up the possibility of creating feedback systems that will automatically enhance or weaken stimulation, responding to the patient’s condition in real time.

In addition to brain data, the researchers assessed participants’ emotional reactions to various images, from neutral to unpleasant. Those who reacted particularly strongly to negative images, such as accidents or injuries, were much less likely to improve after stimulation. This may be another criterion for selecting patients.

The authors of the study emphasize that although DBS is already used in Parkinson’s disease, its use in psychiatry is still at an early stage. The new work is the largest among the studies of simultaneous stimulation of BNST and nucleus accumbens in depression, and it shows that the method is really capable of changing the lives of patients for whom other options have not worked.

At the same time, the team has completed the gold standard, a double—blind randomized trial, the results of which will be published soon. If they turn out to be similar, DBS could become one of the key tools in the treatment of severe depression, where effective solutions are still lacking.