Can electrical stimulation of the brain replace antidepressants

@enjoyman, Geektimes
(for links to sources, see the original article)

Over the past year, research on noninvasive electrical stimulation of the brain has advanced far. Thus, a large-scale analytical study based on 1,412 scientific articles revealed that exposure to the brain with a weak direct current (transcranial direct current stimulation, tDCS) is effective for the treatment of depression and several other mental illnesses.

Moreover, apparently, tDCS is not inferior in effectiveness to standard antidepressants, and in safety it is also significantly ahead of them. Interestingly, a similar electrical stimulation can be used by healthy people to improve their mood and greater resistance to everyday stress.

Considering that in developed countries up to 17% of people suffer from depression at least once in their lives (as, for example, in the USA), and a decrease in mood as a result of depression entails a variety of cognitive impairments: from memory problems to impaired ability to solve problems, scientists suggest the widest potential application of the new technology.

Electrical stimulation of the brain (tDCS) is the effect on the cerebral cortex of a weak direct current through electrodes located on certain areas of the head. Such an effect changes the physiological state of neurons, making them more or, conversely, less prone to arousal. Depending on the location of the electrodes, such stimulation leads to a number of effects: from the relief of chronic pain and the treatment of mental illness in patients, to accelerated learning and improved concentration in healthy people.

To date, more than 15,000 scientific human experiments have been conducted on the effects of tDCS on literally everything from schizophrenia to the treatment of tinnitus. However, the trouble with studies is their strong heterogeneity: different exposure parameters (stimulation time, current strength, etc.) and different quality of studies – from good double-blind placebo-controlled studies to works in which there is not even a placebo group. Attempts to synthesize current knowledge about tDCS have already been made, but they sinned by analyzing studies with different designs and sample sizes.

A large–scale study of a large team of neuroscientists from France, Germany, Switzerland, New Zealand, Italy and Belgium is perhaps the first example of a qualitative understanding of the influence of tDCS on various diseases. How tDCS can improve the cognitive functions of healthy people is the subject of a separate conversation covered earlier.

Electrical stimulation helps with depression, chronic pain and addictions

Scientists analyzed a huge array of tDCS studies: no more, no less than 1,412 articles, in which more than 8000 people participated in total, and chose among them works with only high-quality design.

The experiments had to be with a control group of people (in whom stimulation was simulated to exclude the placebo effect), as well as randomized (that is, the subjects are randomly divided into groups). In all studies, people had to undergo not one tDCS session (which may not be enough for the effect to manifest), but several. In addition, studies in which more than 25 people participated received greater priority, and studies in which there were fewer than 10 participants were not taken into account at all.

Analysis of these studies has shown that tDCS is effective for the treatment of several common diseases: depression, chronic pain and addictions (for example, to alcohol, nicotine and even light drugs), but does not help with chronic tinnitus. Based on these studies, scientists have concluded that electrical stimulation is effective in the case of those diseases when structural restructuring of the brain is not required.

Mechanism of action 

The principle of operation of tDCS is not too complicated. Electrodes applied to the scalp affect the brain with a weak direct current (1-2 milliamps). A positively charged electrode ("anode") reduces the potential difference on the membrane of neurons, which facilitates their excitation in the event of signals from neighboring neurons. A negatively charged electrode ("cathode"), on the contrary, increases the potential difference, reducing the excitability of neurons.

The result of several minutes of electrical stimulation is an increase in the activity of the cerebral cortex area under the anode, which persists for an hour or more after the procedure is completed. In the case of tDCS for several days in a row, changes occur in the neurons of the cortex in the interneuronal contacts – synapses. For example, they can increase in size, which facilitates the transmission of a signal from one neuron to another. This process is called synaptic plasticity, and it is responsible for maintaining the effects of tDCS after the completion of the course of effects.

The principle of treatment of depression 

The principle on which the treatment of depression with tDCS is based is also quite simple. Studies show that in depressed patients, the activity of certain areas of the frontal lobes of the left and right hemispheres differs. Electrical stimulation is designed to compensate for this imbalance. To do this, a positively charged electrode ("anode") is placed over a less active area of the brain, which slightly increases its activity.

The analysis showed that electrical stimulation for 20-30 minutes a day for at least several days in a row leads to a stable improvement in the condition of patients with severe clinical depression. For this, the correct location of the electrodes is critically important. The anode should be located above the left prefrontal cortex (DLPFC) – F3, and the cathode – on the right supraorbital region – FP2. Interestingly, if you shift the cathode a few centimeters higher, the effect disappears.

Scientists have assigned this conclusion "Class B", that is, "the technology is probably effective" and believe that in order to recognize electrical stimulation as uniquely effective, studies should be conducted with a large number of participants. Nevertheless, transcranial electrical stimulation has already been approved for the treatment of depression in Europe.

Electrical stimulation vs antidepressants

Interestingly, a direct comparison of tDCS and some antidepressants shows that electrical stimulation is not inferior to them in effectiveness. For example, a double-blind randomized study by Harvard scientists demonstrated that patients with depression recovered faster after tDCS than after taking fluoxitin, a selective serotonin reuptake inhibitor.

Another study showed that tDCS is not inferior to sertraline, another popular antidepressant. It is important to note that in the case of a combination of both effects (electrical stimulation with an antidepressant), the effect was superior to each of the therapies separately.

However, if the effectiveness of tDCS and antidepressants (at least some) is similar, then electrostimulation is significantly ahead of them in terms of safety. Indeed, the side effects of antidepressants can be very serious (up to obesity, sexual problems and even hallucinations).

The side effects of tDCS are much less significant. Although they were closely monitored in each of the studies, of the undesirable consequences, patients periodically experience only a slight tingling and burning sensation, as well as skin irritation in the areas of electrode attachment.

Cure depression at home?

However, today tDCS technology has one significant drawback. For treatment, patients are forced to go to the clinic for procedures (unlike antidepressants, which can be taken at home on their own).

That is why several companies have taken up the development of portable medical devices for home use. These are, for example, the New York company Soterix Medical and the Korean startup Ybrain. In addition, several non-medical tDCS devices are already being produced, offering the same arrangement of electrodes for depression under the sign of "mood improvement".

Andre Bruoni, a neuroscientist and psychiatrist at the University of Sao Paulo, believes that such devices have 3 potential advantages:

• Price: Since tDCS devices are relatively cheap, people will prefer them to more expensive technology like transcranial magnetic stimulation (TMS).
• Ease of use: Bruoni says startups like Soterix are "developing very safe and reliable devices for home use with almost zero risk."
• Brevity of treatment: tDCS therapy for depression will begin with an intensive course – for example, 2 weeks of daily electrostimulation sessions – after which much rarer sessions will be conducted to maintain the effect. This is a great advantage over antidepressants, which often require courses of 9 months (during which they can cause negative side effects).

TDCS to improve mood?

Interestingly, electrical stimulation from depression ("anode" – on the left dorsolateral prefrontal cortex) can be useful for healthy people. For example, in 2016, a double-blind placebo–controlled study on 66 healthy volunteers showed that electrical stimulation significantly improved the overall mood of the subjects, including - reduced anxiety, depression, hostility to others, reduced fatigue and a feeling of confusion of thoughts.

Another study of the same year, conducted by scientists from Oxford on 60 healthy people, showed that tDCS increases a person's resistance to stress.

Against the background of a constant increase in the number of such studies, a fairly large community of people who use tDCS in everyday life has already formed. On the Reddit website alone, more than 8,000 people constantly share their experience of using tDCS devices, while about 30% have tried to use the technology for depression therapy (other users use tDCS to improve memory, concentration and concentration).

To carry out procedures, people use special non–medical devices – designed for everyday use, which are already being produced in the USA – Thebrainstimulator, Hong Kong – Priormind and since last year – in Russia - Brainstorm Neurostimulator. All of them allow you to place electrodes on several (up to 10) different areas of the head, for various cognitive effects, among which there is an improvement in mood.

A curious fact is that in the first non-medical tDCS device produced by an American company foc.us and designed to improve the reaction and concentration of gamers, the electrodes were positioned precisely to improve mood (from depression):

It is possible that this is why such a device was popular: although it did not directly affect reaction and memory, it improved mood and, due to this, users liked it. However , subsequently foc.us still, I corrected my mistake and such a device is no longer available.

Many scientists, however, are wary of the independent use of tDCS, which is fraught with many mistakes "due to inattention" (for example, the wrong location of the electrodes on the head or too long exposure time – instead of the prescribed 20-30 minutes), which can lead rather to undesirable results. But on the other hand, scientists themselves are already offering people to use tDCS at home as part of scientific experiments, when they are convinced that people fully comply with safety regulations.

Portal "Eternal youth" http://vechnayamolodost.ru  09.02.2017