What is Transcranial Direct Current Stimulation (tDCS)?
tDCS, the technique used in the Flow headset, has a long history. It usually takes researchers several years to find out if a treatment is effective enough to use in medical practices. One study is not enough! On this page, you’ll find some facts about the history of tDCS and a table comparing different types of brain stimulation techniques. Have fun!
A brief history of brain stimulation
Let’s start with a summary of some of the most important discoveries in tDCS history.
Greek and Roman physicians observed that electric currents could relieve headache and joint pain. They used electric discharges from the “torpedo fish”! (Largus, 1529)
The interest in brain stimulation increased among researchers and tDCS was reappraised. Two important studies showed that tDCS could help activate the brain’s cortex. (Priori et. al, 1998; Nitsche & Paulus, 2000)
After that, several studies used tDCS to investigate different brain areas or as a treatment for psychiatric disorders
An RCT* study by Fregni and colleagues showed that tDCS could have antidepressant effects. The group of patients that received tDCS treatment had a 58.5% mood improvement, measured with the Hamilton Depression Rating Scale (HDRS), whereas the placebo group had a 13.1% mood improvement. (Fregni et. al, 2006.)
RCT* studies by Loo and colleagues, Palm and colleagues and Blumberger and colleagues examined the effects of tDCS for depression. The results were included in a meta-analysis** by Brunoni and colleagues in 2016, showing that tDCS was comparable to rTMS and antidepressant medication when treating depression in primary care. (Loo et. al, 2010; Palm et. al, 2012; Loo et. al, 2012; Blumberger et. al, 2012; Brunoni et al., 2016)
Kalu and colleagues performed a meta-analysis** of earlier studies, suggesting that tDCS has antidepressant effects, at the same time noting that future studies should use larger patient samples for clearer results. (Kalu et. al, 2012)
Brunoni and colleagues concluded that tDCS is a suitable treatment for depression and can be used in clinical practice because the technique is noninvasive, has a low rate of side effects, is low-cost and portable.
“tDCS is a technique with a low rate of reported side effects, relatively easy to apply and less expensive than other neuromodulatory techniques — appealing characteristics for clinical use. In the past years, 4 of 6 phase II clinical trials and one recent meta-analysis have shown positive results in ameliorating depression symptoms.”
Brunoni and colleagues conducted an RCT* study. The researchers discovered that combining tDCS and antidepressant medication made both treatments more effective. The main scores on the Montgomery-Asberg Depression Rating Scale (MADRS) differed significantly between the group of participants that received medication and tDCS in combination and the group that received medication only (mean difference: 8.5 points). The scores also differed significantly between the combined treatment group and the group that received tDCS only (mean difference: 5.9 points) and between the combined treatment group and the placebo group (mean difference: 11.5 points). (Brunoni et. al, 2013)
Brunoni and colleagues performed a meta-analysis**, showing that tDCS was comparable to rTMS and antidepressant medication when treating depression in primary care. (Brunoni et. al, 2016)
Through a meta-analysis**, Bikson and colleagues found that tDCS is safe to use and has never been associated with brain damage.
“To date, the use of conventional tDCS protocols in human trials (≤40 min, ≤4 milliamperes, ≤7.2 Coulombs) has not produced any reports of a Serious Adverse Effect or irreversible injury across over 33,200 sessions and 1000 subjects with repeated sessions. This includes a wide variety of subjects, including persons from potentially vulnerable populations.”
Brunoni and colleagues found that 41% of depressed people noticed that at least half of their symptoms disappeared within 6 weeks of using tDCS. Only 22% in the placebo group experienced similar results. (Brunoni et. al, 2017)
Nikolin and colleagues performed a meta-analysis** showing that tDCS is safe to use and that injuries do not increase with higher levels of tDCS exposure. (Nikolin et. al, 2018)
Pavlova and colleagues found that a combination of tDCS and antidepressant medication is an effective treatment for mild to moderate depression. Also, a treatment with 30-minute stimulation sessions is more effective than one with 20-minute sessions. (Pavlova et. al, 2018)
Loo and colleagues conducted an RCT* study and found no difference between depressed participants given active tDCS treatment (2,5 mA) and those given sham tDCS (0.034 mA and two 60-second current ramp ups to 1 and 0.5 mA). According to the researchers, one possible explanation for the finding was that the weak current in the sham group affected participants’ moods. (Loo et. al, 2018)
Mutz and colleagues compared different types of brain stimulation techniques to find out if they should be used as treatments for depression. The researchers found tDCS to be efficacious and a less expensive treatment than TMS, ECT or psychotherapy.
“…we found tDCS to be efficacious across outcomes in both pairwise and network meta-analyses. Given that tDCS tends to be a less expensive treatment than transcranial magnetic stimulation, ECT, or psychotherapy, this finding is particularly relevant for policy makers who might consider tDCS as a clinical therapy outside the research setting.”
Flow Neuroscience introduces the first medically approved tDCS device for home use.
*An RCT (Randomised Controlled Trial) study is a type of research method used to make sure that results are as reliable as possible.
**A meta-analysis is a research method that combines results from multiple studies. This means that the results from a meta-analysis are particularly reliable.
Modern brain stimulation techniques
|What is it called?|
|What is it?||Transcranial direct current stimulation (tDCS) is a non-invasive, non-pharmacological and painless form of brain stimulation.||Transcranial magnetic stimulation (TMS) is a non-invasive and non-pharmacological form of brain stimulation.||Electroconvulsive Therapy (ECT) induces a generalised seizure in the brain to relieve symptoms of severe psychiatric disorders.|
|What drives the stimulation?||Electric current||Electromagnetic induction||Electric current|
|Where is it used?||tDCS is approved for treating depression and chronic pain in the EU, including the UK. It’s available for home use. Flow Neuroscience offers the first medically approved device for at-home treatment||In 2009, TMS was approved by the US Food and Drug Administration (FDA) for depression treatment. Today, TMS is used in hospitals in the UK, the USA and Sweden.||ECT is used both in the EU and the USA to treat the most severe cases of depression. The technique is very different from tDCS and can only be used in hospitals under general anesthesia.|
|How does it work?||tDCS delivers a weak direct current (0,5-2 mA) to specific brain areas via electrodes placed on the scalp. It helps the cortex of the brain become more easily excited. tDCS can be used at home or at health care clinics.||Instead of direct electric current, TMS uses electromagnetic fields to alter the activity in specific areas of the brain’s cortex. TMS is administered by healthcare professionals and doesn’t require anesthesia.||An electric current passes through the brain to induce a generalised seizure in anesthetized patients. The current used in ECT is 400 times stronger than with tDCS and should only be used to treat the most severe cases of depression.|
|What brain area is stimulated?||In the treatment of depression, the electrodes are placed to target the DLPFC (dorsolateral prefrontal cortex) of the brain.||TMS targets basically the same brain area as tDCS in depression treatment, that is the DLPFC (dorsolateral prefrontal cortex).||In the treatment of depression, electrodes are most commonly placed over the temporal cortex of the brain on both sides of the scalp.|
|What are the side effects?||Side effects are less severe than those from medication, TMS and ECT. Side effects include mild stinging sensations under the electrodes and mild headaches that pass after 30 minutes.||Side effects are less severe than those from medication or ECT. Side effects include headaches and a small risk of seizures.||Side effects include confusion, memory loss and physical pain.|
|Is it available for home use?||Yes||No||No|
Why should I trust Flow Neuroscience?
You don’t have to. Flow has been examined by external experts selected by the British Standards Institution (BSI). The Flow headset is CE-marked and medically approved for use in the EU. To get this approval, the manufacturer must prove that the device is clinically equivalent. This means that external experts on brain stimulation and health technology examined the headset and made sure it’s doing the same thing as the devices in the research studies. The CE certification ensures that Flow is based on scientific evidence, that the treatment reduces depressive symptoms and that the headset is safe to use.