The brain runs on electricity. Neurons send each other signals, and their shared rhythm shows up on an EEG as brain waves: beta during normal wakefulness and stress, alpha during relaxed focus, theta during deep relaxation and delta in deep sleep. Modern technologies promise that you will be able to tune this rhythm consciously, without years of meditation. Some of them have high-quality clinical trials behind them, others mainly good marketing. Let us look at which is which.
How to read the numbers: Fact = a finding from research or biology
Without a serious adverse effect
Single-session tDCS in healthy people
Home tDCS in Nature Medicine
Neurofeedback: a mirror for the brain
In neurofeedback, sensors on the head record the brain's electrical activity and turn it into instant feedback. You watch a film, and when the brain produces too many "unfocused" waves, the picture darkens. The brain wants to see the picture, so it gradually learns to switch over. Clinics often start with quantitative EEG (QEEG), a map of brain waves at rest and during tasks, and set up the training according to it.
It has been studied most in ADHD. A meta-analysis of 13 randomised trials with 520 children and adolescents, however, revealed an important detail. Improvement was reported mainly by raters who knew who was receiving the treatment, such as parents (standardised difference 0.35). When the raters did not know, or when neurofeedback was compared with sham training, the difference disappeared. So neurofeedback is not a fraud, but we do not yet know how much of the effect comes from the training itself and how much from expectations, the therapist's attention and a regular routine.
Home EEG headbands work on the same principle, only more simply: at rest you hear birdsong, and when your mind wanders, the sound turns into a storm. As an aid for learning meditation they can be excellent. As a treatment for ADHD or anxiety, they are not.
tDCS: weak current, strong promises
Transcranial direct current stimulation (tDCS) passes a weak current through two electrodes on the head, typically 2 mA in studies. It does not fire neurons, it only changes their readiness: under the positive electrode (anode) they activate more easily, under the negative one (cathode) they are dampened. That is why it matters where you place the electrodes.
The best data are in depression. In a NEJM trial with 245 patients, tDCS was better than placebo but did not match the effect of the antidepressant escitalopram, and it brought more skin redness, tinnitus and nervousness. Two patients developed mania. In 2024, Nature Medicine published a trial with 174 patients who stimulated themselves at home under remote supervision: 30 minutes, at first five times and later three times a week, for 10 weeks. Depression improved by 9.41 points with active stimulation and by 7.14 points with sham. The effect is real, but more modest than advertisements promise, and the placebo effect is strong here.
And what about healthy people who want to be "smarter"? The largest quantitative review of single-session tDCS in healthy adults found no significant effect in any of 59 analyses, including working memory. So if someone sells tDCS as a quick intelligence booster, be sceptical.
With standard protocols (up to 40 minutes and up to 4 mA), no serious adverse effect or permanent injury was recorded in more than 33,200 sessions. Safety, however, applies to certified devices and correct use, not to a home-built circuit with a battery.
I do not recommend home-built devices. A poorly moistened electrode can burn the skin, and with reversed polarity you get the opposite of what you want. If you try tDCS, do so only with a certified device (CE marking as a medical device), according to the instructions, and for depression always in agreement with your doctor.
The vagus nerve through the ear: taVNS
The vagus nerve is the nervous system's main brake. Its implanted stimulator is an approved treatment for severe epilepsy and depression, but it requires surgery. Transcutaneous stimulation (taVNS) therefore tries to stimulate its branch in the outer ear through the skin, with a small electrode on a clip or in an earbud. It is being studied for anxiety, depression, migraine, tinnitus and pain.
A 2020 critical review, however, points out that the mechanism is still largely hypothetical and that there is no firm evidence on the optimal site or stimulation parameters. Each study uses different settings, which makes comparison difficult. Before buying an expensive device, try what costs nothing: slow breathing with a longer exhale, cold water on the face, which triggers the diving reflex, or humming a long tone. These techniques also act through the vagus.
Light on the forehead and sound in the ears
Transcranial photobiomodulation shines red and near-infrared light onto the forehead or head. A 2025 systematic review describes that it increases mitochondrial activity and blood flow in the brain and reports possible benefits for sleep, wakefulness and cognition. The studies are still small, heterogeneous and often pilot studies. It is an interesting field that should be approached with humility. When using it, protect your eyes and follow the manufacturer's time and distance.
Binaural beats work like this: you play a 400 Hz tone into the left ear and a 410 Hz tone into the right, and the brain perceives a pulsation at the 10 Hz difference. It only works with headphones. A meta-analysis of 22 studies found a moderate effect on memory, attention, anxiety and pain perception, with listening before a task giving better results than during it. A systematic review of 14 EEG studies, however, showed that only five confirmed that the brain really "tunes in" to the given frequency, while eight contradicted it. Binaural beats may help you calm down, but the theory of "tuning brain waves" remains uncertain.
Safety and who should be careful
- Epilepsy – rhythmic sound or light stimulation and electrical brain stimulation are not for experimenting without a neurologist.
- Implants – a pacemaker, cochlear implant or metal parts in the head are a reason not to use electrical stimulation without a doctor's approval.
- Bipolar disorder – cases of mania have been described with tDCS, so use it only under a psychiatrist's supervision.
- Pregnancy and children – data on home use are lacking, so avoid it.
- Injured or irritated skin – there is a risk of burns at the electrode sites.
- Depression and ADHD – a home device does not replace treatment. If you want to try it, treat it as an add-on and agree on it with your doctor.
Start with what costs nothing and carries no risk: slow breathing for five minutes a day and regular sleep. If technology appeals to you, the first step is binaural beats through headphones or an EEG headband for meditation. Ten to twenty minutes before work, for two weeks, with notes on how well you focus. Move on to tDCS or taVNS only with a certified device, according to the instructions, and with any illness after consulting your doctor.
- Strong evidence The safety of standard tDCS in studies. A modest effect of tDCS in depression compared with placebo.
- Moderate evidence Binaural beats for anxiety and attention. Neurofeedback for ADHD according to unblinded ratings.
- Weak evidence taVNS for anxiety and depression, and transcranial photobiomodulation for sleep and cognition.
- No evidence Single-session tDCS as an intelligence booster in healthy people and promises of "reprogramming the brain" in a few sessions.
Conclusion
The brain is plastic, and technology really can influence it, only less dramatically than advertising claims. tDCS has the best data in depression and is safe when used correctly; neurofeedback is an interesting form of training with a questionable difference from placebo; binaural beats are a cheap way to calm down; and taVNS and photobiomodulation are still at an early stage. Buy certified devices, measure your results and remember that the most powerful tools for rebuilding the brain, namely sleep, movement and meditation, are available to you for free.
