Transcranial electrical stimulation (tDCS, tACS, tRNS)

1. Introduction

Version followed: prescription home-use and clinic tDCS for depression, as described in the US FDA premarket approval for the Flow FL-100 (PMA P230024, approved 8 December 2025) and its Summary of Safety and Effectiveness Data (SSED); NICE HealthTech guidance HTG382 (published 26 August 2015 as IPG530); and the IFCN/ESBS-endorsed low-intensity transcranial electrical stimulation safety guideline (Antal et al., 2017) with its 2025 update draft. The psychotherapist's role is written as synthesis. Regulatory status checked October 2026.

What it is. Transcranial electrical stimulation (tES) passes a weak electrical current through electrodes on the scalp. The aim is to change brain activity without surgery and without inducing a seizure. EU device law groups three forms together as equipment that applies electrical currents to modify neuronal activity in the brain: transcranial direct-current stimulation (tDCS, a constant current), transcranial alternating-current stimulation (tACS) and transcranial random-noise stimulation (tRNS) [source: NAMSA summary of Implementing Regulation (EU) 2022/2346]. The safety guidelines cover all three. They report no serious adverse events attributed to low-intensity tES in their reviewed data, and mild, short-lived sensations and headache are common [source: Antal et al. 2017 abstract; Antal et al. 2025 update draft].

How change is thought to happen. In depression, tDCS is offered as a non-drug biological treatment that is used alongside, or instead of, medication and psychotherapy. The FDA SSED lists CBT, interpersonal psychotherapy and problem-solving therapy among the alternatives [source: FDA SSED P230024]. The proposed mechanism is a modulation of cortical activity. The sources for this guide do not set out a mechanism in more depth, so it is not described here [uncertain].

Who delivers it. A psychotherapist does not prescribe, set or deliver tES. In the US the Flow FL-100 is prescription-only and is used at home under a licensed clinician's supervision. The prescribers named are psychiatrists, primary care physicians and psychiatric nurse practitioners [source: Flow US patient page; HLTH, 9 Sept 2026]. In the NHS, NICE describes tDCS as usually given by a trained clinician, though patients can self-administer it [source: NICE HTG382]. Research tES should be given by trained personnel [source: Antal et al. 2025 update draft]. This guide is written for the psychotherapist who works alongside the prescriber or neuromodulation team. Its scope is referral, psychoeducation, consent support, monitoring, crisis planning and integrating psychotherapy. It contains no stimulation settings, electrode positions, durations or session numbers, and no instructions for self-use.

Regulatory status (as of October 2026, per the sources named)

2. Framework

The device sources do not describe a psychotherapy protocol. The phases below organise the psychotherapist's work around the treatment as the FDA SSED and NICE describe it. Counts and timings of stimulation are deliberately omitted [synthesis, built on the cited sources].

Phase A: Considering treatment (before referral).

• Goals: recognise when a client with depression might benefit from a medical review that includes neuromodulation options; give balanced information; refer.
• Format: within ordinary therapy sessions.
• Move on when: the client has agreed to a review by a prescriber, and you have sent the referral with the client's consent [synthesis].

Phase B: Assessment, prescribing and consent (prescriber-led).

• What happens: the prescriber confirms the diagnosis and the episode severity. They check that the client falls within the indication and is not treatment-refractory to medication [source: FDA PMA database]. They screen for contraindications (open wounds, broken or damaged skin at the electrode site, metallic skull reconstruction at the electrode site) [source: FDA SSED] and decide whether to prescribe.
• In the NHS: clinicians must make sure patients understand the uncertainty about efficacy and receive clear written information, and outcomes are audited [source: NICE HTG382].
• Your goals: support understanding and shared decision-making; pass on relevant history with consent.
• Move on when: the prescriber has prescribed and the client has given informed consent [synthesis].

Phase C: Starting and the active course (home or clinic).

• How it is delivered: in the pivotal US trial, research staff supervised the first use directly. After that, they monitored use through a clinician web portal. The clinician uses the portal to monitor headset use and to set the stimulation parameters. A smartphone app guides preparation and session control, shows the schedule, tracks use, sends reminders and collects weekly self-rated depression scores [source: FDA SSED]. The commercial software is described as controlling stimulation timing and restricting excessive use. It reports adherence and symptom progress to the prescriber [source: HLTH].
• Your goals: continue or begin psychotherapy; monitor mood, side effects and engagement; pass concerns to the prescriber; keep the crisis plan current.
• Format: your usual session rhythm, with a brief device check-in at each session [synthesis].

Phase D: End of the course and afterwards.

• Context: NICE notes uncertainty about how long the effect lasts. It also reports that in one follow-up, a sustained response was much less common in treatment-resistant depression [source: NICE HTG382].
• Your goals: relapse prevention, consolidating psychological gains, and planning with the client and prescriber what happens if symptoms return.
• Move on / end when: the usual criteria for ending therapy are met [synthesis].

Who decides. Starting, pausing, stopping, restarting and any change to the device programme are prescriber decisions [source: Flow US patient page; FDA SSED]. Your role is to observe, inform and support.

3. Guiding principles

• Device decisions sit with the prescriber. Never suggest a change to settings, frequency of use or electrode handling, and never suggest stopping or starting. Route every such question to the prescriber [synthesis; prescription status per FDA PMA database].
• Stay within your competence. You are not the device trainer. Refer the client to the prescriber or the company's support for technical questions [synthesis].
• Be honest about the evidence. NICE judges the efficacy evidence limited, with uncertainty about mode of administration, number of treatments and how long effects last. Present tDCS as one option among several, not as a cure [source: NICE HTG382].
• Psychotherapy remains a treatment in its own right. The FDA SSED lists CBT, IPT and problem-solving therapy as alternatives. Offer integration rather than replacement [source: FDA SSED].
• Consent is a process. Support the client to understand the indication, the alternatives, the common and rare effects, and their right to stop at any time by contacting the prescriber [source: NICE HTG382 on consent; synthesis].
• Watch mood closely. Manic and hypomanic episodes appear in the tDCS literature [source: NICE HTG382; Antal et al. 2017; FDA SSED]. Screen for a switch at every contact [synthesis].
• Skin injury is the most practical physical risk. In the pivotal trial, burns occurred when pads had dried out. The company states that reused or dried-out pads are linked to burns [source: FDA SSED; Flow US patient page]. Ask about skin. Never advise on pad technique; refer the client to the prescriber and the instructions for use.
• Pass information on promptly and with consent. Agree in advance what you will share with the prescriber, and how [synthesis].
• No do-it-yourself stimulation. Neither encourage nor tolerate unsupervised or consumer brain stimulation as a substitute for treatment. See the harm account below [source: Wurzman et al. 2016 via Penn Medicine release; synthesis].
• Respect privacy. App and portal data about use and mood reach the prescriber [source: FDA SSED; HLTH]. Check the client understands this [synthesis].
• Stay inside the indication. The approval covers adults with a current moderate to severe depressive episode. Under-18s, and people with treatment-refractory depression, fall outside it [source: FDA PMA database]. If a client in these groups asks about the device, refer the question to the prescriber [synthesis].

4. Intervention inventory

Part A describes how the treatment is delivered, as regulators and guidelines state it. It is for your understanding only; none of it is an instruction. Part B covers the psychotherapist's own interventions.

A1. Prescription home-use tDCS: Flow FL-100 (USA)

• Purpose / when used: treatment of moderate to severe major depressive disorder in the current episode. It can be used alone or alongside medication, in adults 18 and over who are not treatment-refractory to medication [source: FDA PMA database P230024].
• How it is delivered (descriptive):
  • A prescriber assesses the person, either their own clinician or a clinician on the company's telehealth pathway, and prescribes the device. It is then shipped to the person's home [source: Flow US patient page; HLTH].
  • The person uses a headset at home, guided by a smartphone app that shows the schedule, tracks use, sends reminders and collects weekly self-ratings of depression.
  • The prescriber monitors use and sets the programme through a clinician web portal [source: FDA SSED].
  • The software restricts excessive use and reports adherence and symptom progress to the prescriber [source: HLTH].
• Contraindications in the SSED: open wounds, broken or damaged skin at the electrode site; metallic skull reconstruction at the electrode site. The full warnings and precautions are in the device labelling [source: FDA SSED]. The labelling and the company's safety page are not drawn on in this guide, so check them before relying on this list [uncertain].
• Groups excluded from the pivotal trial (not studied, not formal warnings):
  • people with epilepsy or seizures;
  • people with brain or skull implants, other active implants, or shrapnel or ferromagnetic material in the head;
  • people with a history of mania, hypomania or psychosis;
  • people with recent suicidal behaviour;
  • pregnancy or breastfeeding;
  • prior serious cardiac events;
  • intractable migraine;
  • use of medicines that affect cortical excitability, such as benzodiazepines. [source: FDA SSED]
• Adverse effects as officially described:
  • Common: skin redness, itching, burning sensation, headache, scalp pain, sleepiness, trouble concentrating during stimulation and acute mood change. Skin redness was clearly more common with active treatment.
  • Skin burns: two first-degree burns, both in users of dried-out pads, healed without lasting effects.
  • Serious events: none were attributed to the device. The SSED reports no hypomania, mania or suicidality in the trial.
  • From other studies and the literature: blurred vision, dizziness, nausea, migraine, neck pain, vivid dreams, a raised heart rate and mania or hypomania. [source: FDA SSED] The company's description adds skin dryness, transient headache, and stinging or itching at the site. It links burns to reused or dried-out pads, which it advises against [source: Flow US patient page].
• Watch for (as the therapist): the client using the device in ways other than prescribed; new skin marks; mood elevation or worsening. Pass each to the prescriber (see B5).

A2. Clinic or NHS tDCS for depression (UK)

• Status: NICE allows use only with special arrangements for clinical governance, consent and audit or research [source: NICE HTG382].
• Arrangements NICE requires:
  • inform the trust's clinical-governance leads;
  • make sure patients understand the uncertainty about efficacy, and give them clear written information plus NICE's public information;
  • audit and review the outcomes of every patient treated. [source: NICE HTG382]
• Adverse events NICE lists:
  • manic or hypomanic episodes (mostly in a group also taking sertraline);
  • skin redness and lesions, headache, itching, tingling, burning, light-headedness, blurred vision, nausea and sleepiness;
  • one case report of panic attacks. Many of these also occurred with sham treatment. Specialist advisers raised further possible but unreported risks: seizures, worsening depression, interference with implanted devices and facial muscle twitching. Flashes of light were also reported anecdotally [source: NICE HTG382].
• Who delivers it: usually a trained clinician; self-administration is possible [source: NICE HTG382].

A3. tES in research settings (tDCS, tACS, tRNS)

• Safety position:
  • The 2017 guideline found no serious adverse events in its reviewed sessions. It described moderate events such as tDCS skin burns as rare and usually linked to poor electrode-skin contact. It documented a small number of manic or hypomanic episodes in depressed patients, with causality hard to establish [source: Antal et al. 2017 abstract].
  • The 2025 update draft reports a consistent safety profile across tDCS, tACS and tRNS. It states that skin lesions are not expected with verified devices, good technique and intact skin, and that past lesion reports were linked to poor technique or equipment. It recommends trained personnel, screening and adverse-event questionnaires, and electrodes verified for tES (not recording or TENS electrodes). It notes that data on long-term and repeated use are incomplete, and that modelling suggests children may receive stronger cortical fields because of thinner skulls [source: Antal et al. 2025 update draft].
• For you: a client taking part in a trial has a study team and a consent document. Route effects and concerns to that team, and to the ethics contact named in the document if needed [synthesis].

A4. Consumer and non-medical brain-stimulation products

• EU: these products are regulated under MDR Annex XVI with common specifications. They must carry a non-medical-purpose label and may not claim clinical benefit [source: NAMSA].
• Elsewhere: non-therapeutic devices are sold over the counter, mainly online, often under less stringent oversight, and DIY construction guides are widely available [source: MDS blog, 2017].
• For you: none of these is a treatment for depression or any other condition. See B9 and the harm account.

B1. Recognising when to suggest a medical review and referral

• Purpose / when: a client with a moderate to severe depressive episode who has not improved enough, prefers non-drug options, or asks about brain stimulation [synthesis; indication per FDA PMA database].
• Steps:
  1. Review the course of the episode and the treatments tried so far.
  2. Ask about the client's preferences, and what they have read or bought.
  3. Explain that only a prescriber can assess whether tDCS, other neuromodulation such as TMS or ECT, or a change of medication is suitable. The SSED lists these as alternatives [source: FDA SSED].
  4. With consent, write a referral that summarises symptoms, risk, psychotherapy to date, any history of mania or hypomania, seizures, head injury or implants, and skin conditions on the scalp.
  5. Agree how the prescriber's decision will reach you. [synthesis]
• Example language (illustrative): "There are medical options beyond what we can do here, including brain-stimulation treatments. I'm not the person who can say whether one fits you, but I can help you get a proper review. Would that be useful?"
• Watch for:
  • Expectations of a quick fix, or a wish to avoid the prescriber by buying a device online. If you hear the second, go to B9.
  • Good sign: the client books the review with realistic hopes.

B2. Psychoeducation about transcranial electrical stimulation

• Purpose / when: the client is considering tES, has been offered it, or has started.
• Steps:
  1. Explain in plain terms that a weak current is passed through scalp electrodes; the person stays awake, and no seizure is induced [synthesis from source descriptions].
  2. State the indication and status where the client lives: in the US, a prescription device for adults with a current moderate to severe depressive episode [source: FDA PMA database]; in the NHS, used only with special arrangements because of limited evidence [source: NICE HTG382].
  3. Name the common effects: skin redness, itching, tingling or burning sensations, headache and sleepiness. Name the rare but important risks: skin burns and mood elevation such as hypomania or mania [source: FDA SSED; NICE HTG382].
  4. Explain that the prescriber, not the client or you, controls the programme [source: FDA SSED].
  5. Clarify that consumer "brain-boosting" products are not the same thing (see B9).
• Example language (illustrative): "Most people feel some tingling or itching, and the skin may go red. The things to tell your prescriber straight away are any sore or broken skin, or feeling unusually high, wired or unable to sleep."
• Watch for: misunderstandings, such as fear of "electric shock treatment" or a belief that more use is better. Correct these neutrally. Good sign: the client can name what to report and to whom.

B3. Supporting informed consent and shared decision-making

• Purpose / when: before the prescriber obtains consent, and whenever the client is unsure.
• Steps:
  1. Help the client write down their questions for the prescriber, for example: Am I within the indication? What are the alternatives? How is my use monitored? Who sees my app data? What should I do if my skin is damaged or my mood changes? How do I stop?
  2. Explore values and fears.
  3. Check what the client understood from the written information. NICE requires clear written information on the uncertainty of efficacy [source: NICE HTG382].
  4. Never make or steer the decision.
  5. If capacity seems impaired, for example by severe depression or psychosis, tell the prescriber. [synthesis]
• Example language (illustrative): "Let's list what you'd want to know before deciding, so you can ask your prescriber directly."
• Watch for:
  • Consent given under pressure from family or a wish to please.
  • Good sign: the client can explain the reasons for their own choice.

B4. Supporting a client who uses a prescribed home device

• Purpose / when: throughout the home course.
• Steps:
  1. At each session, do a brief check-in: Is it going as your prescriber planned? Any problems with the app or headset? How is your skin? How is your mood?
  2. Explore ambivalence and missed use using motivational, non-directive questions.
  3. Problem-solve routines, such as when and where use fits into the day, without touching the prescribed parameters.
  4. Send technical and dosing questions to the prescriber or the device support service.
  5. If the client wants to use the device more, use it differently, share it, or stop, encourage them to contact the prescriber first. Remind them that the software is designed to restrict excessive use [source: HLTH]. [synthesis]
• Example language (illustrative): "It sounds like part of you wants to keep going and part of you is fed up. What's getting in the way? Whatever you decide about the device itself, your prescriber needs to be part of that conversation."
• Watch for: the device becoming a source of guilt or avoidance; use outside the prescription. Good sign: steady engagement, and problems raised early.

B5. Monitoring and passing on adverse effects and mood changes

• Purpose / when: every contact during the course and shortly afterwards.
• Steps:
  1. Ask about skin redness, soreness, blistering or broken skin at the electrode sites; burns are linked to dried-out or reused pads [source: FDA SSED; Flow US patient page]. Also ask about headache, scalp pain, sleepiness, problems concentrating, blurred vision, dizziness, nausea and vivid dreams [source: FDA SSED].
  2. Screen for mood elevation: less need for sleep, racing thoughts, pressured speech, irritability, risk-taking [synthesis; mania and hypomania reported per NICE HTG382 and Antal et al. 2017].
  3. Screen for worsening depression, suicidal thoughts, panic or agitation. NICE lists a panic case report and possible worsening of depression [source: NICE HTG382].
  4. Use a standard symptom measure in your own sessions if that is your practice. The app already collects weekly self-ratings for the prescriber [source: FDA SSED].
  5. Agree in advance, with consent, how you will contact the prescriber: same day for skin injury, signs of mania or hypomania, or a rise in suicide risk; routinely for minor effects [synthesis].
  6. Document what you observed and whom you told.
• Example language (illustrative): "You've slept three hours a night this week and feel unusually energised. That's something your prescriber needs to know today. Can we call together now?"
• Watch for: under-reporting, because clients may fear losing the treatment. Normalise reporting. Good sign: problems are passed on promptly and the prescriber responds.

B6. Crisis and safety planning

• Purpose / when: before the course starts, reviewed during it and after it ends.
• Steps:
  1. Update the written safety plan: warning signs, coping strategies, people to contact, professional and emergency contacts, and steps to make the environment safer.
  2. Add a device-specific line: whom to call about skin injury or a mood switch (prescriber, out-of-hours service).
  3. Remind the client that the device is not an emergency treatment; in a crisis, local emergency pathways apply.
  4. Recent suicidal behaviour was an exclusion criterion in the pivotal trial [source: FDA SSED]. Share current risk with the prescriber, with consent or as your duty requires. [synthesis]
• Example language (illustrative): "If things get worse, the headset isn't the plan. Let's make sure your safety plan says exactly who you call."
• Watch for: hopelessness if the client sees no early change. Good sign: the client can say their plan aloud.

B7. Integrating psychotherapy before, during and after the course

• Purpose / when: throughout.
• Steps:
  1. Continue or start an evidence-based psychotherapy such as CBT, IPT, problem-solving therapy or behavioural activation; the SSED lists these as treatments in their own right [source: FDA SSED].
  2. Ask whether the device programme includes its own app-based content. Flow's earlier UK app offered guidance based on behavioural activation (sleep, exercise, eating, meditation) [source: Wareable, 2019]. Agree with the client how you will avoid duplicated or conflicting homework.
  3. Use any early lift in energy to schedule valued activities.
  4. Frame change as the client's own work, not only the device's. [synthesis]
• Example language (illustrative): "If you start feeling a bit more energy, let's use it. What's one thing you've been putting off that matters to you?"
• Watch for: passive waiting for the device to work. Good sign: the client takes up activity and skills alongside the device.

B8. Support after the course ends

• Purpose / when: at the end of the course and over the following months. NICE notes uncertainty about how long the effect lasts [source: NICE HTG382].
• Steps:
  1. Review gains and early warning signs.
  2. Build a relapse-prevention plan that includes when to go back to the prescriber.
  3. Tell the client that any further courses are the prescriber's decision.
  4. Plan booster or follow-up therapy sessions. [synthesis]
• Example language (illustrative): "What would tell you, early, that the depression is creeping back, and who would you contact first?"
• Watch for: relapse, or disappointment if the course did not help. Process this, and support a further medical review.

B9. Responding when a client mentions DIY or consumer brain stimulation

• Purpose / when: the client is using, building, buying or considering a non-prescribed device, or follows online communities about it.
• Steps:
  1. Ask without judgement: what, why, how often, and with or without anyone overseeing it.
  2. Check for skin injury, headaches and changes in mood, sleep or cognition. Researchers warn that effects can be unpredictable and long-lasting, and that boosting one ability may impair another [source: Wurzman et al. 2016 via Penn Medicine release].
  3. Explain the difference from prescribed treatment (see the harm account).
  4. Encourage the client to stop unsupervised use and to see their doctor, especially if they are injured or their mood has changed.
  5. Address the underlying need, such as untreated depression or performance pressure.
  6. Never give or discuss technical information. [synthesis]
• Example language (illustrative): "I'm glad you told me. I can't advise on how to use it, and the researchers who study these devices warn that home use can have effects nobody can predict. Can we look at what you're hoping it will do for you, and get you checked by a doctor?"
• Watch for: concealment and minimising. Good sign: the client stops, gets checked, and engages with a supervised option.

B10. Communication, documentation and data privacy

• Purpose / when: throughout.
• Steps:
  1. Obtain written consent for two-way contact with the prescriber.
  2. Record device-related observations factually.
  3. Explain to the client that app and portal data on use and mood go to the prescriber [source: FDA SSED; HLTH].
  4. Do not ask to view or manage the client's device account. [synthesis]
• Example language (illustrative): "Your prescriber can see how often you use the headset and your weekly mood scores. Are you comfortable with that? Shall we talk about what else you'd like me to share?"
• Watch for: confusion about who holds clinical responsibility. Settle it explicitly.

5. Handling problems

The device sources do not address psychotherapy problems. Everything in this section is synthesis unless a source is given.

• No improvement, or the client feels stuck. Validate the disappointment. NICE describes the efficacy evidence as limited and uncertain [source: NICE HTG382]. Encourage a prompt prescriber review of the overall treatment plan, and strengthen the psychotherapy itself through activation, problem-solving and attention to interpersonal stressors. Never suggest using the device more or differently.
• Ambivalence or missed use. Explore the obstacles: the time it takes, discomfort, embarrassment, doubt. Problem-solve routines, and tell the prescriber about persistent non-use rather than "fixing" it yourself. Respect a decision to stop, but encourage the client to make it with the prescriber.
• The client wants to use it more, use it differently, or buy a second device. Say clearly that the programme is set by the prescriber [source: FDA SSED]. Explore the urgency behind the wish, which may be hopelessness or perfectionism, and refer the question back to the prescriber. If the client is considering a non-prescribed device, go to B9.
• Skin injury. Advise the client to contact the prescriber now and to follow the device's instructions. Do not advise on wound care or pad technique; if the injury needs medical attention, the GP or urgent care. Burns have been linked to dried-out or reused pads [source: FDA SSED; Flow US patient page].
• Emerging hypomania or mania. Contact the prescriber the same day, and use urgent pathways if the client's safety or judgement is compromised. Mania and hypomania have been reported with tDCS for depression [source: NICE HTG382; Antal et al. 2017]. In the US pivotal trial, a history of mania or hypomania was an exclusion criterion [source: FDA SSED].
• Worsening depression or rising suicide risk. Follow standard risk assessment and the safety plan (B6), and inform the prescriber. The device is not a crisis intervention.
• Overwhelm with the technology. Some clients are overwhelmed by the app, notifications or self-ratings. Help them prepare questions for the device support service or the prescriber, and keep your sessions free of technical tasks.
• The client treats the device as a replacement for therapy, or therapy as a replacement for the device. Revisit the shared formulation. Psychotherapy and the device are complementary options, and the choice is the client's, made with the prescriber [source: FDA SSED lists psychotherapy as an alternative].
• Rupture after you raise a concern with the prescriber. Repair openly: explain your duty and your care, and acknowledge the client's fear of losing the treatment. The best protection is agreeing information-sharing in advance (B10).
• The client is outside the indication or in a group that was not studied. This includes under-18s, people with treatment-refractory depression, pregnancy, epilepsy, implants and a history of mania [source: FDA PMA database; FDA SSED]. Tell the client that these are questions for the prescriber. Do not reassure them yourself.
• Confusing names. The FDA's generic name for the FL-100 is "cranial electrotherapy stimulator to treat depression" [source: FDA PMA database]. This does not make other cranial electrotherapy stimulation products, whose claims are contested, equivalent to it. Encourage clients to check the exact device and the indication with their prescriber.
• Cross-border buying and international telehealth. Status differs by country (see the regulatory table). A device bought abroad or online, without a local prescriber, carries the risks described in the harm account.

Harm account

This section concerns do-it-yourself (DIY) and consumer use of transcranial electrical stimulation, not prescribed treatment. It deliberately contains no technical detail.

What was actually done

• Since the mid-2010s, healthy and unwell people have stimulated their own brains without clinical oversight. They used either homemade devices or devices sold directly to the public. Non-therapeutic devices were sold over the counter, mainly online, and DIY construction guides were widely available [source: MDS blog, 2017].
• Who used them, and why. Wexler surveyed 339 people who had bought a device from one of seven companies selling to the public as of June 2016, mostly in North America [source: Wexler 2018].
  • The typical user was a highly educated, affluent man in his forties who saw himself as an early adopter of technology.
  • About three quarters used it for cognitive enhancement and about 40% for treatment; roughly a third were self-treating depression.
  • A minority reported cumulative use far beyond research protocols.
  • Many stopped because it did not work, or never used it because they had no guidance.
• How the products were sold. They were marketed for gaming and as "brain tuning" lifestyle tools [source: Palm & Feichtner 2020].
• The researchers' response. In July 2016, 39 researchers led by Rachel Wurzman and Roy Hamilton (University of Pennsylvania) published an open letter to DIY users in Annals of Neurology. They warned of hidden and unknown risks [source: Penn Medicine release, 2016].

How it caused harm

• Skin burns.
  • Ten users in Wexler's survey reported serious skin burns [source: Wexler 2018].
  • The clinical literature explains the mechanism. Uneven contact between skin and electrode creates current bridges. The contact medium can dry out, and skin can touch the bare electrode, which causes thermal damage. A burn from a dried-out sponge produced a second-degree lesion that healed with a small scar [source: Palm & Feichtner 2020].
  • The authors conclude that incorrect application of the electrodes is the main factor. They state that the standards needed to prevent burns are probably met reliably only in specialised services, not at home, and that cranial skin burns can signal misuse [source: Palm & Feichtner 2020].
  • Safety guidelines likewise attribute skin lesions to poor technique, poor equipment or poor electrode-skin contact [source: Antal et al. 2017; Antal et al. 2025 update draft]. Even under regulated, supervised conditions, burns occurred when pads dried out [source: FDA SSED].
• Unpredictable brain effects. The 2016 open letter warns:
  • risks from cumulative use over years are unknown;
  • stimulation may affect untargeted regions, and improving one ability may impair another;
  • changes may be "long-lasting, for better or worse";
  • up to 30% of people respond in the opposite direction to others;
  • small differences in setup can have large, unexpected effects, and more is not necessarily better;
  • what a person does during stimulation can change the outcome. [source: Penn Medicine release on Wurzman et al. 2016]
• Mood effects. Manic and hypomanic episodes have been reported in depressed patients receiving tDCS even under research conditions [source: Antal et al. 2017; NICE HTG382]. Unsupervised users have no one screening for this [synthesis].
• Other effects.
  • Headache, fatigue and other short-lived effects are common [source: Antal et al. 2017; MDS blog].
  • NICE's advisers listed seizures, worsening depression and interference with implanted devices as possible but unreported risks [source: NICE HTG382].
  • A neuroethicist warned that unsupervised use might cause serious effects such as temporary respiratory paralysis. This is a warning, not a documented case [source: MDS blog, 2017].
  • No deaths are reported in the sources [uncertain].
• Who was most at risk.
  • People with neurological or psychiatric disorders, metallic intracranial implants or skull defects [source: MDS blog].
  • Children: safety data are limited [source: MDS blog], and modelling suggests stronger cortical fields because of thinner skulls [source: Antal et al. 2025 update draft].
  • People self-treating depression, who may delay effective care [synthesis].

Recognising it today

• Features:
  • a device bought online or built at home, used without a prescription or clinician;
  • marketing about focus, gaming, learning, "brain tuning" or performance;
  • settings or routines taken from forums or videos;
  • escalating or very frequent use;
  • sharing devices. [source: MDS blog; Palm & Feichtner 2020; Wexler 2018; synthesis]
• Physical signs: round or stripe-shaped sores, crusts or scars on the scalp or forehead [source: Palm & Feichtner 2020].
• Labelling: in the EU, consumer brain-stimulation equipment must state that it has a non-medical purpose and may not claim clinical benefit. Any health claim on such a product is a warning sign [source: NAMSA].
• Red flags in a colleague's or service's practice [synthesis]:
  • offering or selling stimulation devices without a prescriber;
  • advising clients on settings;
  • claiming benefits beyond the approved indication;
  • no contraindication screening, monitoring or adverse-event reporting.
• How legitimate use differs:
  • a prescriber, an approved indication and contraindication screening;
  • a programme set and monitored by the prescriber through a clinical platform;
  • official safety information and informed consent;
  • in the NHS, governance and audit arrangements. [source: FDA SSED; NICE HTG382]

What to do instead and how to help those harmed

• Safer alternatives:
  • evidence-based psychotherapy (CBT, IPT, problem-solving therapy);
  • prescriber-led medication review;
  • regulated neuromodulation (TMS, ECT, prescribed tDCS where available) after medical assessment. [source: FDA SSED alternatives list] For cognitive-enhancement motives, explore sleep, stress, workload and any untreated condition [synthesis].
• Assessment of an affected client [synthesis]:
  • ask without judgement what was used, for how long, and the reasons;
  • check for skin injury and refer to the GP, dermatology or urgent care;
  • screen for mood elevation, worsening depression, suicidality, headaches and changes in cognition or sleep, and refer for a medical or psychiatric review as needed;
  • ask about seizures or loss of consciousness and arrange urgent medical assessment if present;
  • address shame and the needs behind the use.
• Treatment: standard care for any condition you find. Psychotherapy can address performance pressure, self-treatment patterns and mistrust of services [synthesis].
• Children: treat use by a minor as a safeguarding and medical matter, and involve the parents or carers and a doctor [synthesis; limited paediatric safety data per MDS blog].
• Reporting and ethical duties [synthesis; check local guidance]:
  • encourage, or with consent make, an adverse-incident report through the device-reporting system in your jurisdiction, for example the MHRA's scheme in the UK or FDA MedWatch in the US;
  • document the injury and the advice you gave;
  • raise a colleague's unsafe practice with your professional body or regulator;
  • never supply, recommend or troubleshoot devices or protocols.

Sources

Sources

• FDA Premarket Approval database entry P230024: Flow FL-100
• FDA Summary of Safety and Effectiveness Data, P230024 (Flow FL-100)
• Flow Neuroscience: US patient page
• Patient Care Online: FDA clears first at-home brain stimulation device for major depression (11 Dec 2025)
• HLTH: Flow Neuroscience launches FDA-approved at-home depression treatment in the US (9 Sept 2026)
• Wareable: Flow headset gets UK approval (4 June 2019)
• NICE HTG382 (formerly IPG530): Transcranial direct current stimulation (tDCS) for depression
• Antal et al. (2025 draft): Low intensity transcranial electric stimulation: safety, ethical, legal regulatory and application guidelines (2017–2025: an update), IFCN-hosted manuscript
• Open Access LMU record: Antal et al. 2017, Clinical Neurophysiology 128(9):1774–1809 (abstract only)
• Wexler A. (2018) Who uses direct-to-consumer brain stimulation products, and why? Journal of Cognitive Enhancement 2:114–134
• Palm U, Feichtner KB. (2020) Skin burns from transcranial electrical stimulation. Cutis 105(2):E14–E15 (MDedge)
• Penn Medicine news release (July 2016): Neuroscience researchers caution public about hidden risks of self-administered brain stimulation
• Movement Disorders Society Scientific Issues Committee blog (2017): Transcranial Direct Current Stimulation (Lou, Chen, Dubljević)
• NAMSA: EU Commission publishes MDR implementing regulation for devices without a medical purpose (Annex XVI)

Further reading (not drawn on)

• Wurzman R, Hamilton RH, Pascual-Leone A, Fox MD (2016). An open letter concerning do-it-yourself users of transcranial direct current stimulation. Annals of Neurology. Content is taken from the Penn Medicine release and the MDS blog reference list; volume and pages not verified [uncertain].
• Flow FL-100 labelling (FDA P230024C/D) and the Flow US safety page: not drawn on. The full warnings and precautions should be checked there [uncertain].
• Commission Implementing Regulation (EU) 2022/2346: summarised via NAMSA [uncertain].