Flow Glossary
Understanding your treatment starts with understanding the language. This glossary explains the key terms you may come across when learning about brain stimulation, depression treatment, and how Flow works.
Understanding your treatment starts with understanding the language. This glossary explains the key terms you may come across when learning about brain stimulation, depression treatment, and how Flow works.
Anhedonia is when you lose the ability to feel pleasure or interest in things you used to enjoy — a core symptom of depression. Brain stimulation targeting the mood-regulation area may help improve your ability to experience positive emotions again.
These FDA terms do not mean the same thing. PMA devices are FDA approved, 510(k) devices are FDA cleared, and De Novo requests are generally described as granted.
At-home brain stimulation means you can use your treatment device at home, without clinic visits. Flow was designed for safe home use, with built-in safety features and a guided app programme.
Behavioural activation is a technique in the Flow app that encourages you to re-engage with mood-boosting activities, even when motivation is low. It works alongside brain stimulation to help build healthier daily habits.
BSI is an independent organisation that can assess whether a medical device meets certain regulatory requirements in the EU and in Great Britain. BSI can also certify a company’s quality management system to ISO 13485.
A cathode refers to the negatively charged electrode used in tDCS
The CE mark shows that a medical device meets EU requirements for safety and performance and can be sold in the EU. For some devices, this includes independent review by a Notified Body.
Your body has a 24-hour internal clock controlling sleep, energy, and mood. Depression can disrupt this clock. Improving depression symptoms with Flow may help your natural rhythms get back on track.
Flow is a Class IIa medical device, which means it is considered medium risk and must meet specific regulatory requirements before it can be sold.
Class III is the FDA’s higher-risk device category. These devices usually need the strongest level of review before they can be marketed in the United States.
Clinical validation can mean many things, but for us, it’s about proof. We use this term to show that Flow has been rigorously tested through scientific research and real-world use, earning its place as many clinicians preferred treatment option and it’s place within national healthcare systems.
CBT is a widely used talking therapy for negative thought patterns. Some research suggests using tDCS alongside CBT may improve outcomes, as brain stimulation may make the brain more receptive to learning.
Comorbidity means having more than one health condition at the same time. Depression often occurs alongside other conditions inculding both mental and physical symptoms. Flow is still suitabable and safe to use if you have other coditions but you should always consult with your doctor.
Contraindications are reasons why a treatment will not be suitable. Because Flow is very safe, there are only two contraindications:
1. If skin issues are present at the electrode site such as open wounds, broken skin, or damaged skin
2. If there has been skull reconstruction at the electrode site such as a metalic or plastic implant
Cortical excitability describes the state of how active the outer layer of your brain is. In depression, certain areas become less active. Flow gently increases activity in these cortical areas to help restore normal function.
De Novo is an FDA pathway for new types of lower- to moderate-risk medical devices when there is no similar device already on the market.
The DLPFC is the part of the brain near the front at the top of the forehead where the electordes site. This area of the brain supports emotional regulation, decision making, and focus. Research shows it’s often less active when depressed. Flow targets this area to increase cortical activity and help improve mood.
A double-blind study is where neither participants nor researchers know who gets the real treatment vs sham. This prevents bias. Flow has been tested this way.
Can be a biological symptom of depression where you wake up very early and are unable to get back to sleep. Flow has been shown to improve the quality of sleep quickly (as little as 3-weeks) in people experiencing depression.
ECT is a treatment reserved for severe depression using application of an electrical current under general anaesthesia to induced a controlled seizure. This can be effective and in some cases life-saving but it is usually reserved for very severely unwell people, requires hospital admission or visits, and may cause memory side effects. Flow is a far gentler home-based treatment that uses a tiny electrical current (400x less than ECT) to increase brain activity in key areas relating to mood regulation. Flow has been offered in some cases to avoid ECT successfully.
Effect size measures how much difference a treatment makes regardless of the sample size of a clinical trial. It does this by reflecting the clinical significance. Flow’s clinical trial showed a meaningful treatment benefit — significantly greater improvement than sham.
Flow’s headset has built-in, pre-positioned electrodes and app guidance to help ensure stimulation reaches the correct brain area — no measuring or positioning needed.
Emotional blunting is a symptom where people feel emotionally numb or flat. Emotional blunting can be caused by depression, anxiety disorders, or other conditions and may also be a side effect from medication. Emotional blunting whilst taking antidepressant medication is widely reported by 40 to 60% of antidepressant users. Flow works differently from medication and does not cause this.
This means a company tells the FDA where its device business is based and which devices it makes or distributes. It does not mean the FDA has approved or cleared the device.
EUDAMED is the European database for medical devices. It helps regulators, healthcare professionals and the public access information about devices sold in the EU.
The FDA is the U.S. government agency that regulates medical devices, medicines and some other health products.
A 510(k) is an FDA review pathway used for some medical devices. A device that passes this route is described as FDA cleared.
Flow received FDA approval through the Premarket Approval, or PMA, route. This is the FDA review pathway used for certain higher-risk medical devices.
Flow uses a closed protocol — number and length of session are fixed and can’t be changed unless prescribed by a doctor. This safety feature ensures you always receive the correct stimulation dose.
High-functioning depression describes people who maintain their daily lives and may appear otherwise “fine” while still experiencing persistent low mood and other symptoms beneath the surface. This form of depression can often remain undiagnosed yet causes significant distress and poor quality of life for the individual.
Home-based neuromodulation means receiving brain stimulation at home rather than at a clinic. Flow combines medical-grade technology with app-based guidance for safe, convenient treatment.
Hypersomnia means excessive sleeping or daytime sleepiness — a less well-known depression symptom. Flow may help improve energy and sleep patterns by regulating brain areas involved in mood and alertness.
Insomnia and depression are closely linked — poor sleep worsens depression and depression causes poor sleep. Flow addresses underlying brain circuits involved in both, which is why many users report improvements in both.
MADRS is a standardised questionnaire measuring depression severity. Flow uses the self-report version (MADRS-S) in the app to track your progress. Lower scores mean fewer symptoms.
After initial treatment, you can continue using Flow several times a week to maintain progress and help prevent depression returning. This is also known as the Strengthening Phase.
After your first 3 weeks of 5 stimulations per week, you move to fewer sessions per week. This reduced schedule supports continued benefits while fitting your routine.
The MDR is the main EU regulatory framework for medical devices. In Great Britain, medical devices are regulated under the UK Medical Devices Regulations 2002, as amended.
Flow has been officially reviewed and cleared by health authorities. In Europe: CE-marked and UKCA-certified. In the US: FDA cleared — the first tDCS device to receive this clearance for at-home depression treatment.
Medication tapering means gradually reducing antidepressant dose under doctor supervision. Some people use Flow as support during tapering. Important: never change medication without consulting your doctor.
A meta-analysis combines results from many clinical trials for a bigger, more reliable picture. Multiple meta-analyses confirm tDCS efficacy for depression.
The MHRA is the UK regulator for medicines and medical devices.
Neuromodulation is a treatment category which uses a range of techniques to influence activity in specific brain areas. Flow uses tDCS, a form of non-invasive neuromodulation gently targeting a mood-regulating area of the brain, without surgery or medication.
Neuroplastic priming is the idea that brain stimulation may make your brain more receptive to learning and change — potentially making therapy, TMS, and even ECT more effective. This is an exciting area of ongoing research.
Neuroplasticity is your brain’s ability to form new connections throughout life. Flow promotes neuroplasticity by repeatedly stimulating key areas, helping build healthier patterns.
Neurotransmitters are chemicals like serotonin, dopamine, noradrenaline that are released in the brain and can affect mood. Many antidepressants target these neurotransmitters, attempting to alter their levels. Flow works differently — by changing activity in key brain areas and how they communicate, which in turn may also indirectly improve chemical balance.
Flow has been used and studied within 5 NHS Trusts and NHS Practitioner Health in the UK. Published evaluations show Flow works in real NHS clinical settings — GP practices, community mental health teams, and specialist services.
Starting out with Flow, you will be asked to go through a short guided setup. This setup supports learning more about how to use your device and introduces the Flow treatment.
An OTC device can be bought without a prescription. Flow is available over the counter in relevant markets where this route is permitted.
Pharmacotherapy means treating a condition with medication — for depression, usually antidepressants. Flow offers a different approach by stimulating the brain directly rather than through medication.
Polypharmacy means taking multiple medications simultaneously. This can introduce complications as some medications cannot be taken together and typically the side effect burden is greater when taking more than 1 medication. Flow offers a non-medication based treatment that can be easily combined with other treatments without the risk of interactions. Furthermore, it has been shown in studies that combining Flow with antidepressant medication helps improve outcomes from depression.
After a device goes on sale, the manufacturer must continue monitoring its safety and performance to help make sure it remains safe and effective in real-world use.
Post-synaptic modulation is one way brain stimulation creates lasting effects — by changing how brain cells respond to signals, creating longer-term mood improvements.
A premarket submission is the application a company sends to the FDA before selling certain medical devices in the United States.
An RCT is the gold standard of clinical research — participants randomly get real treatment or placebo (also known as a sham), so researchers can be confident improvements are genuine. Flow has been tested this way.
Real-world evidence comes from studying how treatments work for everyday people not just those participating in academic studies. Flow has been used in a range of real world settings including NHS services and we have published data from thousands of real world Flow users confirming positive outcomes.
Remission means depression symptoms have reduced to the point where you no longer meet the clinical criteria for depression or in other words, are depression free. Over half of Flow users achieved this in just 10 weeks in the Flow clinical trial.
Response rate refers to the number of people who experience a 50% reduction in their depressive symptoms. In Flow’s clinical trial, nearly 2 in 3 (64%) experienced this level of improvement after 10 weeks.
Sham stimulation is the tDCS placebo or a “dummy” version of the device. It is used only in trials and helps to confirm improvements are caused by the stimulation, not expectations.
An adverse event is any unwanted side effect during treatment. With Flow, the most common side effects are very mild — slight tingling, temporary skin redness, or a light headache. These go away quickly. Serious side effects with properly used tDCS are extremely rare.
Sleep architecture is the structure of your sleep stages throughout the night. Depression disrupts this. Improving depression with Flow may help normalise sleep patterns.
Sleep hygiene means daily habits for better sleep — regular bedtime, limiting screens, comfortable environment. The Flow app includes sleep hygiene tips alongside treatment.
SSRIs are the most commonly prescribed antidepressants. Whilst useful; for many, nearly 2/3 of patients experience major side effects from antidepressants and these drugs do not achieve full remission for over 70% of patients. Alternative treatment options are desperately needed. Flow offers another treatment choice.
In FDA language, this means a device is similar enough to an existing legally marketed device to use the 510(k) route.
The Flow app lets you regularly track depression symptoms through a simple questionnaire, helping you see progress over time.
tACS is another form of brain stimulation that uses an alternating current (vs direct current in tDCS). tACS is currently used mostly in research and has less depression focused evidence than tDCS.
tDCS is a safe, non-invasive technique delivering gentle electrical current to specific brain areas through electrodes placed high up on the forehead. Flow uses tDCS to target the mood-regulating area to treat depression.
The protocol refers to the treatment schedule: 5 sessions per week for 3 weeks, followed by 3 sessions per week. Each session is 30 minutes. When using Flow over-the-counter, settings are fixed to the protocol used in our RCT. However, personalised settings are possible when working with your clinician.
TMS is another brain stimulation treatment using magnetic fields instead of electrical currents. TMS can be effective but requires in-clinic visits, is time-intensive, and can be very expensive. People who respond to TMS may need to return for maintenence treatment in the longer term to prevent relapse. Flow offers a more accessible, convenient, and affordable option.
Each Flow stimulation session is 30 minutes. The first 3 weeks include 5 sessions/week followed by 3 sessions per week. You can use Flow while reading, watching TV, or relaxing.
TRD is when depression doesn’t improve after trying at least two different antidepressants. TRD is more common than many realise. Flow offers an evidence-based treatment option for depression which works through a different mechanism to medication. Flow can be used as a stand alone treatment or in combination with medication. There are many cases where patients have responded well to Flow despite poor response to other treatments.
The UKCA mark shows that a product meets the rules for sale in Great Britain. For some medical devices, this includes assessment by a UK Approved Body.