Transcranial direct current stimulation (tDCS) devices

Transcranial direct current stimulation is the latest iteration of non-surgical brain stimulation devices which began with electroconvulsive therapy (ECT) and then repetitive transcranial magnetic stimulation (rTMS).

A meta-analysis of randomised controlled trials (Mutz Reference Mutz, Vipulananthan and Carter2019) showed that, although ECT and rTMS were superior to tDCS in terms of response, tDCS was itself effective. Importantly though, tDCS had significantly less cost and risks associated with it, compared with ECT or rTMS.

Flow is a device that uses tDCS. It has a headset that connects to an app. This can be set up to connect with a clinician to monitor response and adherence but this is not essential.

The manufacturers of Flow state that the device is being used in 5 NHS trusts and in over 500 private clinics.

A recent double-blind controlled study of tDCS involving 174 participants with severe depression showed significant improvement, with 57.5% gaining remission and a 64.2% response rate by 10 weeks, as measured on the Montgomery-Åsberg Rating Scale for Depression (MADRS), with minimal side-effects, which included transient local skin irritation, redness and trouble concentrating (Woodham Reference Woodham, Selvaraj and Lajmi2025).

Non-invasive vagus nerve stimulation (nVNS) devices

The vagus nerve’s role in modulating mood, inflammation and autonomic function has been increasingly recognised. Invasive VNS, initially developed for epilepsy, demonstrated efficacy in treatment-resistant depression as early as 2007 (Kaniusas Reference Kaniusas, Kampusch and Tittgemeyer2019). However, the need for surgery limited accessibility.

Contemporary non-invasive VNS (nVNS) devices – such as NuroSym (transcutaneous auricular VNS), Pulsetto (transcutaneous cervical VNS) and Amofit S (cervicothoracic vagus electromagnetic stimulator) – address these barriers. By stimulating peripheral vagal branches, these wearables aim to modulate central mood circuits without requiring surgical implantation. Although mechanisms remain incompletely understood, evidence continues to build for applications across depression, post-traumatic stress disorder, inflammatory syndromes and chronic pain (Kaniusas Reference Kaniusas, Kampusch and Tittgemeyer2019).

All are examples of VNS devices available to the public without prescription. Side-effects are again purported to be local and transient, with few relative contraindications, including recent myocardial infarction or severe cardiac disease.

Other devices

There are other devices on the market that claim to target sleep and anxiety, such as CalmCarry and Sensate. CalmCarry is a small handheld device that uses microcurrents to stimulate pressure points in the hand, while Sensate emits ‘infrasonic waves’ conducted by the sternum, which the device sits on, to produce thoracic resonance. The aim of Sensate is to reproduce the effect of chanting to promote relaxation and sleep. The device links to a specially made audio track via Bluetooth. There are no scientifically published papers on eithers use.

Personal experiences

As a psychiatrist, I came across these devices on social media. I bought a Sensate device in 2022 when struggling with perimenopausal insomnia and anxiety. I found it helped me to get off to sleep and was extremely pleasant and relaxing to use. I justified the cost as being the same amount as a day spa. It has lasted longer and I still enjoy using it regularly.

Then, following difficulties my husband was having with nocturia from selective serotonin reuptake inhibitor medication, leading to poor adherence, I purchased a Flow device for him. My husband, a medic, had been taking an antidepressant since developing a moderate to severe depressive illness a few years ago. This had been picked up late because of its insidious onset as well as his introverted character and fear of stigma, which prevented him seeking help. The medication had undoubtably worked but use of Flow was followed by my husband’s mood returning to a new normal and it became clear to me that he had probably been dysthymic for a number of years. His sense of humour and fun returned, with much more motivation and family and social engagement. To my shame, I had attributed his loss of these to life changes, COVID-19 and stressors, and this is a good reminder of why psychiatrists cannot effectively assess or treat their own family members.

From my husband’s point of view, the device allowed him to avoid having to go back to the general practitioner, which he found embarrassing, intrusive and time consuming. The only side-effect experienced was a local stinging sensation during sessions. Interestingly, he did not notice any particular change to his mental state or function but equally, he did not really have much insight when he was profoundly depressed in the past. My husband has not used the free psychological package that is offered in parallel with Flow or properly engaged with the MADRS monitoring, which he finds repetitive. He has also drifted with adherence to the three times weekly sessions. These are aspects that I expect would change if there were professional oversight. However, this would be at the expense of cost, convenience and personal feelings of stigma and shame for him. He has, however, been clear that if both treatments were equally efficacious, that he would choose Flow over an antidepressant.

Professional considerations

The power of placebo, particularly in psychiatry, is well-known to me but these experiences made me want to learn more about such devices and consider whether, and how, to share this knowledge with patients in my professional capacity. For potential patients, to whom these devices are being marketed directly, the fact that you can seek ‘effective’ treatment free of concerns about judgement or stigma from others (including health professionals) and within the privacy of your own home is very alluring. The price point, in comparison with private psychiatric treatment or even wellness products and services, is less or equivalent, especially if you consider that you can use the device repeatedly for future episodes or relapse.

From a medical point of view, thinking about where these devices fit into current treatment guidelines is essential to realise any potential benefits to patients as well as the health service. This is especially the case with the Flow tDCS device, given the growing evidence base and use in the private sector and some NHS teams. For elderly patients with depression, who are already on multiple medications for comorbidity, or pregnant or breastfeeding women, this could become treatment of first choice. The National Institute for Health and Care Excellence (NICE) last reviewed the evidence for tDCS use a decade ago (NICE 2015). This now feels very out of date, especially as the guidance assumes healthcare professional oversight and consent before its use.

Although this paradigm shift may make some psychiatrists anxious, it is also an exciting time for patients and doctors to have an effective third option, in addition to what has traditionally been available. However, it is important that these third treatment options, once evidence of efficacy is available, are equally available to all who could benefit. We should be concerned that, with current NHS finances and a tendency for the NHS to be a late adopter of anything new, these devices may be available only to self-funders in the private sector or via NHS research hubs.

I also wonder what will happen if doctors do not proactively absorb this alternative therapeutic option into their practice. History shows us that where there is a gap, someone will step in to fill it. At the moment it is companies directly marketing the devices to individuals. Given their low risk and no requirement for medical prescription, they could easily be integrated into psychologists’ or wellness practitioners’ scope of practice as another non-medication option. This could lead to further public perception of a gap between the medical profession and others, with further negative labelling of doctors by some as ‘only’ being interested in prescribing drugs as well as beholden to the drug companies. Allowing non-medical practitioners to promote or oversee neuromodulator use could parallel the adverse health consequences of injectibles being used by non-medically trained aesthetic practitioners in unregulated environments.

A final concern is that the direct advertising to the public (potential patients) and purchase (self-prescription) of these devices, in combination with stigma of mental illness and difficulty accessing expertise in current healthcare services, may lead to them being used inappropriately. This will lead to self-diagnosis, inappropriate self-treatment and missed serious pathology. Unregulated use of devices may delay diagnosis and effective treatment, particularly where there are complex or unrecognised comorbid conditions.

Summary

The development of a third treatment option for mental illness, separate from talking therapies and medication, is an exciting development for all with an interest in mental health conditions. However, as these are relatively low-cost devices that do not require prescription or medical oversight, there are risks and benefits that may not yet have been realised, both to potential patients and to the medical profession. These devices represent a paradigm shift in patient autonomy, direct patient marketing and the role of the psychiatrist in the treatment of some mental health conditions.