Current landscape of newer non-invasive brain stimulation in psychiatric disorders across South Asia

Abstract

Non-invasive brain stimulation (NIBS) has been an increasingly used therapeutic modality for neuropsychiatric disorders in recent decades. This review attempts to discuss the extent of use (availability of facility, indications of use, amount of research) of various newer NIBS techniques in the management of psychiatric disorders in the South Asian countries till date (i.e., 2025). In South Asia, particularly in India, there has been a notable rise in the use of NIBS treatment methods. Among these, the most prominent techniques are Repetitive Transcranial Magnetic Stimulation (rTMS) and Transcranial Direct Current Stimulation (tDCS), both of which demonstrate encouraging results with minimal side effects. Over the past decades, research into non-invasive neuromodulation has expanded significantly, although it remains predominantly centered in India. This growing body of evidence underscores the potential of these techniques to transform the treatment landscape for psychiatric conditions, offering a hope for patients seeking alternatives to conventional therapies. As interest in neuromodulation continues to grow, the future seems promising for the integration of these advanced modalities into clinical practice.

INTRODUCTION

South Asia contains eight countries, that is, Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Sri Lanka, and Pakistan with low and middle-income country (LMIC) backgrounds.[1] It is a densely populated region with about 2 billion people, covering 15% of the world’s population.[2,3] There are dissimilarities among the countries regarding religion, population density, and language, however, there are similarities regarding mental health services like the income category of the countries, low budget in mental health, inadequate human resources, inequitable distribution of service providers, high treatment gap, huge out-of-pocket expenses, high stigma, and help-seeking from traditional healers.[3] The prevalence of psychiatric disorders among adults was 14.2% (12.9%–15.7%), indicating that about 180 million population have psychiatric disorders with some variations among the countries.[4,5] Among the disorders, depression, anxiety, substance use disorders, and psychosis are the most common burdensome disorders in the region.[6] The region also incurs a high suicide burden and about 30% of global suicides happen in the countries.[7]

The available mental health services deal the persons with psychiatric disorders following the biopsychosocial model based on the availability, and affordability of patients. In many countries, healthcare systems are prompt in adopting new treatment modules to keep pace with advancements in the health sector. This timely integration is essential for ensuring that patients receive access to the latest medical practices and technologies, ultimately contributing to improved health outcomes and enhanced quality of care. Non-invasive brain stimulation techniques are increasingly being used for a spectrum of neuro-psychiatric disorders across the globe; however, the services are limited to mostly the developed and developing countries; the common indications being mood disorder, anxiety disorder, schizophrenia, obsessive compulsive disorder, neurocognitive disorder, and substance use disorder.[8,9,10,11,12]

Neuromodulation techniques, especially electroconvulsive therapy (ECT) a widely used technique for the treatment of various psychiatric disorders in South Asia.[13] However, newer techniques like non-invasive brain stimulations (NIBS) have yet to gain traction in South Asian countries except India, perhaps, due to the demand for additional training and resources which are already scarce state. Little is known about the use of NIBS, their response, acceptance of patients, expense bearing, challenges faced by individual countries, status of research, and gaps comparing among the countries of South Asia. Therefore, we aimed to explore the spectrum of NIBS (except ECT) in South Asia and how it has been utilized to identify gaps. We purposefully avoided ECT, in this article as there are already existing publications that discusses the trend of use of ECT in South Asia. This review aims to explore the status of various newer NIBS techniques in the management of psychiatric disorders across South Asian countries till 2025, with a focus on their availability, clinical indications, and research evidence. This review will help gauge the status quo and determine further ways ahead in the region.

SEARCH STRATEGY

We conducted an extensive search using popular web databases such as Google and Bing, as well as research databases like PubMed, Scopus, and Google Scholar (as of March 2025). Our focus was on the availability, clinical indications, and published research on newer non-invasive brain stimulation techniques, including Repetitive Transcranial Magnetic Stimulation (rTMS), Transcranial Direct Current Stimulation (tDCS), photobiomodulation, and transcutaneous auricular vagus nerve stimulation, and trigeminal nerve stimulation in South Asian countries such as Afghanistan, Bangladesh, Bhutan, Maldives, India, Nepal, Pakistan, and Sri Lanka. All articles were manually screened for relevance. We had also hand-searched the websites of the medical institutions and online resources to check for the availability of newer NIBS facilities country-wise, and communicated with the researchers/academicians of the representative countries.

OVERVIEW OF NEWER NON-INVASIVE BRAIN STIMULATION IN PSYCHIATRIC DISORDERS

Therapeutic neuromodulation, as defined by the International Neuromodulation Society, involves intentionally modifying neural activity. This is achieved through the targeted application of varied stimuli, such as electrical or chemical methods, to specific areas within the nervous system. The goal of this intervention is to ameliorate symptoms and restore functionality in individuals affected by neurological and psychiatric illnesses.[14] Neuromodulation strategies are generally divided into two categories: those that require invasive procedures and those that are non-invasive. While invasive techniques, including implanted Vagus Nerve Stimulators (VNS) and Deep Brain Stimulation (DBS) systems, have received approval for managing conditions like treatment-resistant depression and obsessive-compulsive disorder that have not responded to other treatments,[15,16] their use is limited by the inherent challenges of surgical interventions. In contrast, NIBS offers a non-invasive means to modulate brain function. These techniques enhance neuroplasticity, influence the release of neurotransmitters, and affect overall brain activity with other varied actions. In addition to avoiding the risk of surgery, it typically carries a lower risk of serious side effects, is readily available and less costly than its invasive counterparts, and is often convenient to administer in outpatient settings.[12]

A classification of these techniques based on their mechanisms of action is presented in Table 1. Stimulation based on electrical currents includes ECT. This established approach for treating severe depression works by inducing controlled seizures, thereby enhancing the brain’s capacity for synaptic plasticity.[17] Other electrical methods, grouped under the umbrella of Transcranial Electrical Stimulation (tES), encompass tDCS, Transcranial Alternating Current Stimulation (tACS), Transcranial Random Noise Stimulation (tRNS), and Transcranial Pulse Current Stimulation (tPCS). These techniques use weak electrical currents to subtly alter neuronal excitability, causing subthreshold modulation of the resting membrane potential.[18] NIBS techniques utilizing magnetic fields, such as rTMS, Theta Burst Stimulation (TBS), and Deep TMS, employ electromagnetic induction to generate electrical currents within the brain. These currents can either amplify or suppress neuronal activity and have the capacity to directly trigger action potentials.[15] Sensory electric-based techniques, including the Vagus Nerve Stimulation (VNS), exert influence over key neurotransmitter systems that play a role in both mood regulation and cognitive processes.[19] The use of ultrasonic waves, particularly with Transcranial Low-Intensity Focused Ultrasound (tLIFU), enables the precise modulation of activity in brain structures, even at considerable depths.[20] Thermal stimulation, also known as Transcranial Temperature Modulation (TTM), affects neuronal metabolism, neurotransmitter function, and inflammatory processes by inducing localized changes in temperature.[21] Techniques based on light, such as Transcranial Photo biomodulation (tPBM) and Near-Infrared Stimulation (NIRS), have shown potential for boosting neuroplasticity and enhancing cognitive performance.[22] Transcutaneous trigeminal nerve stimulation has also found to have neuromodulator effect, has been explored for its potential role in several psychiatric disorders, trigeminal neuralgia and epilepsy.[23,24]

Table 1.

Various non-invasive neuromodulation techniques with their mechanism of action (Adapted from)[18,19,20,25,26,27,28,29,30,31,32]

Different Types of Stimulation	Different NIBS modalities	Mechanism of action
Transcranial electrical stimulation	tDCS	•Anodal stimulation produces depolarization, whereas cathodal stimulation produces hyperpolarization, which ultimately result in excitatory and inhibitory response, respectively. •tDCS induces long-lasting synaptic potentiation via augmented BDNF secretion or secondary to gene transcription secondary to tDCS •Change the balance between excitatory and inhibitory inputs via the change in levels of multiple neurotransmitters like GABA, Glutamate, Dopamine, Serotonin, Ach, and so on. •Increase blood flow around the stimulation site, and induce subsequent metabolic changes •Beyond local effects, connectional effects of tDCS have also been implicated in network-level changes •It might also elicit changes in non-neuronal tissues in the brain, including endothelial cells, lymphocytes, or glial cells
	tACS	Delivers low-intensity alternating current to the brain. The primary mechanisms include: •Entrainment of Endogenous Brain Oscillations: the process where externally applied alternating current synchronizes with the brain’s natural oscillatory activity •Resonance Effect: If the applied frequency matches or is close to the natural oscillatory frequency of a brain region, it can enhance or alter the strength of those brain waves
	tRNS	•tRNS applies random electrical stimulation that fluctuates over time, following a Gaussian white noise distribution without a constant or preferred direction. There is no long-term shift and no compensation is needed. •This makes tRNS unique because it can influence brain activity without “forcing” neurons into a new state •Stochastic Resonance (SR): “Noise Boosts Signals”- SR is a phenomenon where adding a small amount of noise can enhance weak signals •May cause repetitive Na+ channel openings, leading to membrane depolarization and long-term potentiation (LTP)-like effects
	tPCS	Delivers pulsed electrical currents to modulate neuronal activity •Biphasic pulses tend to have a more dynamic effect with less polarization •Monophasic pulses may have both dynamic and static effects, leading to more lasting excitability changes
Magnetic field-Based Stimulation	rTMS	•Changes in synaptic plasticity, long term potentiation/Long term Depression produced by Low frequency and High Frequency rTMS respectively (via NMDA and AMPA receptors→changes in Ca2 signaling) •Produce changes in levels of neurotransmitters- GABA, Glutamate, Dopamine, Serotonin, Ach •Anti-inflammatory action, changes in blood flow •Upregulates CB1 receptor expression and endocannabinoid levels •HF-rTMS increases BDNF expression in the hippocampus, which may contribute to its antidepressant effects. •BDNF also activates downstream pathways, like ERK1/2 signaling, enhancing plasticity, and promoting neuronal repair •The differential effects on Immediate early genes (IEG proteins e.g., zif268 and c-fos) and CaBPs suggest that rTMS protocols operate through diverse neurobiological pathways. This specificity might underlie their distinct therapeutic impacts
	TBS	TBS mimics the natural interaction between theta and gamma rhythms through a specific pattern of pulses •TBS modulates NMDA and AMPA receptors to mimic LTP (iTBS) or LTD (cTBS), with calcium signaling as the key mediator •TBS reduces GABA-B receptor-mediated inhibition during theta-rhythm stimulation, enhancing excitatory potential and facilitating plasticity
	d TMS	Uses specialized coils to reach deeper brain structures
	MST	The induction of a seizure occurs through high-frequency, rTMS rather than electrical stimulation in ECT
	LI- rTMS	Uses lower magnetic field strength than traditional rTMS to modulate cortical excitability with reduced side effects, useful for chronic pain and neurorehabilitation.
Sensory-Based Electrical Stimulation	tVNS	Stimulates Vagus nerve through the neck (involving both sensory and non-sensory fibers)
	taVNS	Stimulates the ear’s auricular branch of vagus
Ultrasonic Waves-Based Stimulation	LIFU	Uses precise, low-energy ultrasound waves to target very small and deep brain regions. •Acoustic Radiation Force: Sound waves exert constant pressure on cell membranes, altering ion channel conformation. •Mechano-sensitive Ion Channels: LIFU activates certain ion channels, influencing neural excitability. •Lipid Rafts Hypothesis: Pressure on the membrane might reorganize lipid rafts, affecting neurotransmitter release
Thermal Stimulation	TTM	Alters neural activity through localized cooling or heating, potentially modulating metabolism, neurotransmitter function, and neuroinflammation
Light-Based Stimulation	tPBM/NIRS	Uses red/near-infrared light to •Enhance mitochondrial function (cytochrome C oxidase) •Increase ATP production •Improve cerebral blood flow, and •Reduce oxidative stress •Potentially beneficial for neurodegeneration and cognitive enhancement

BDNF: Brain Derived Neurotrophic Factor; GABA: Gamma-amino-butyric acid; AMPA: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; NMDA: N-Methyl D-Aspartate; ATP: Adenosine Tri-Phosphate; LTP: Long-Term Potentiation; LTD: Long-Term Depression; CB1: Cannabinoid 1; iTBS: intermittent Theta Burst Stimulation; cTBS: Continuous Theta Burst Stimulation; HF rTMS: High Frequency rTMS; tDCS: Trans cranial Direct Current Stimulation; tACS: Transcranial Alternating Current Stimulation; tRNS: Trans cranial Random Noise Stimulation; tPCS: Transcranial Pulse Current Stimulation; rTMS: Repetitive trans cranial magnetic stimulation; TBS: Theta Burst Stimulation; dTMS: Deep Trans cranial Magnetic Stimulation; MST: Magnetic Seizure Therapy; ECT: Electro-Convulsive Therapy; LI-rTMS: Low Intensity Repetitive transcranial magnetic stimulation; tVNS: Trans cutaneous Vagus Nerve Stimulation; taVNS: Trans Auricular Vagal Nerve Stimulation; LIFU: Transcranial low-intensity focused ultrasound; TTM: Trans cranial Temperature Modulation; tPBM: Trans cranial Photo biomodulation; NIRS: Near-Infrared Stimulation

As NIBS strategies are advancing, they offer effective and safer options for the treatment of a broad spectrum of neuropsychiatric and neurological conditions. When a patient has undergone a comprehensive multidisciplinary evaluation, neuromodulation therapy may be a viable option—either to enhance the effects of existing treatments when a partial response is observed, when the condition has proven resistant to other therapies, or in situations where a rapid therapeutic effect is desired. The safety and effectiveness of interventions such as ECT, rTMS, tDCS, and sensory stimulation have been firmly established across diverse patient populations, with only a limited number of precautions and relative contraindications that need to be considered.[25]

Non-invasive brain stimulation in psychiatric disorders: Status in Afghanistan

After thorough searches on major platforms such as Google, Bing, and research databases including PubMed, Scopus, and Google Scholar, we found no information about the availability of non-invasive brain stimulation techniques like rTMS, tDCS, or other similar methods in Afghanistan. As of March 2025, ECT remains the sole neuromodulation option available in Afghanistan for treating psychiatric disorders.

Non-invasive brain stimulation in psychiatric disorders: Status in Bangladesh

Psychiatric services were started in Bangladesh in 1957 with the establishment of Pabna Mental Hospital. ECT was available since the early days in the country. However, utilization of it has significantly reduced in the recent decades and the services have been used rarely in a few hospitals.[33] Neuromodulation techniques are yet to gain popularity among the psychiatrists, services providers, hospital authorities, and patients. There are no available neuromodulation services at government level. Private initiatives have been noted and available services are spreading based on private initiatives. The TMS was started in 2016, as the first noted neuromodulation technique in Bangladesh at a private medical college setting that has been ceased later. However, rTMS facility has been started by another private mental hospital in Dhaka. The Institute of Neuro Development and Research (INDR) has facilities for VNS and rTMS for persons with autism. No traces were noted regarding tDCS and taVNS in Bangladesh.[33]

Non-invasive brain stimulation in psychiatric disorders: Status in Bhutan

After extensive web-search in popular databases like Google, Bing and research databases like PubMed, Scopus, and Google Scholar, we did not find any information regarding availability of non-invasive brain stimulation techniques like rTMS, tDCS and other forms of non-invasive brain stimulation in Bhutan. ECT is the only neuromodulation facility available till date (March 2025) in Bhutan for the management of psychiatric disorders.

Non-invasive brain stimulation in psychiatric disorders: Status in India

Institutes using non-invasive brain stimulation techniques in India

Non-invasive brain stimulation devices have been available in India for over a decade. Most of the studies using rTMS and other tES neuromodulation techniques have been conducted at institutions such as the National Institute of Mental Health and Neurosciences (NIMHANS), All India Institute of Medical Sciences (AIIMS) New Delhi, Central Institute of Psychiatry Ranchi, Kasturba Medical College Manipal, Post Graduate Institute of Medical Education and Research (PGIMER) Chandigarh, and King George’s Medical University (KGMU) Lucknow.[34,35] Some of these institutes also have facilities for neuro-navigation-guided target localization. In addition, several other government and private institutions across the country offer clinical services and are actively involved in research using non-invasive brain stimulation techniques.

Stimulation tools and parameters

The growth of non-invasive brain stimulation techniques in India is comparable to that of Western literature. The initial rTMS studies have used conventional stimulation parameters such as high frequency (>5 or 10 Hz) and low frequency (1 Hz or less) stimulation. With the advancement in the stimulation parameters, recent Indian studies have also used theta burst (50 Hz) stimulation in continuous and intermittent forms, with more daily sessions in accelerated protocols.[34] Studies have used various coil types, including conventional figure-of-eight, double-cone, and the newer H coils.

Similarly, there has been an advancement in the use of tDCS devices in the country. Initial tDCS studies from India reported using 25–35 cm² electrode sizes.[36] Most of the studies used 2-mA for 20 min. Subsequent studies reported using High-Definition Transcranial direct current stimulation with a 4×1 ring electrode montage using sintered Ag/AgCl ring electrodes of radius 6–12 mm.[37] Researchers have tried to explore the feasibility of using home-based tDCS devices for patients with persistent auditory hallucinations.[38]

Training in non-invasive brain stimulation

There are no dedicated training courses for non-invasive brain stimulation in India. NIMHANS offers a post-doctoral fellowship course on non-invasive neuromodulation. However, many societies and organizations offer hands-on training workshops for psychiatrists at various conferences nationwide, including The Neuromodulation Society (India), the Neuromodulation specialty section of the Indian Psychiatry Society and the Neuromodulation Society—Indian chapter of the International Neuromodulation Society.

Laws, regulations and guidelines related to non-invasive brain stimulation

The Mental Health Care Act 2017 of India does not explicitly mention or regulate the use of non-invasive neuromodulation techniques, except for ECT. Comprehensive clinical practice guidelines on the therapeutic use of rTMS[39] and tDCS[40] are available. These guidelines suggest that the provision of rTMS involves an rTMS physician and rTMS operator. rTMS physician is usually a psychiatrist with a deep understanding of neuromodulation, and an rTMS operator can be a non-medical or paramedical staff member trained in administering rTMS and alerting the psychiatrist when necessary.

Non-invasive brain stimulation equipment available in India

Most neuromodulation devices used in Western countries are also being utilized in Indian settings, although their availability is limited to only a few centers. Commonly used rTMS equipment in various Indian settings includes Magstim, Neurosoft, MagVenture, and Deep TMS (Brainsway).[34] Among tES devices, commonly used ones in India include Soterix tDCS, Starstim (Neuroelectrics), the Neurostim tDCS device by Neurosoft, and the NeuroConn DC Stimulator Plus.

Indian research on repetitive transcranial magnetic stimulation (rTMS)

In India, maximal evidence with rTMS is in schizophrenia, followed by obsessive-compulsive disorder (OCD), depressive disorders, migraine, substance use disorders (SUD), mania, panic disorder, and fibromyalgia. Most studies used traditional high or low-frequency stimulation; a few used theta-burst stimulation protocols. Most studies targeted the dorsolateral prefrontal cortex; other areas stimulated were supplementary motor area, orbitofrontal cortex, temporoparietal cortex, cerebellar vermis, anterior cingulate cortex, and dorsomedial prefrontal cortex. Stimulation intensity ranged from 70% to 120% of the resting motor threshold (RMT).[41]

In within-group efficacy meta-analyses, active rTMS was found to be an effective adjunct treatment in the management of schizophrenia,[42,43,44] obsessive-compulsive disorder,[45,46,47,48] and depressive disorders,[49,50,51] with mostly large effect sizes (ES).[41] Encouragingly, in all these disorders, the treatment benefits maintained post-cessation of treatment until the end of follow-up (2–12 weeks), with large ES. Likewise, augmentation with rTMS also significantly reduced craving in SUD with a large effect size, both at the end of treatment and end of follow-up.[52] However, between-group analyses revealed that active rTMS was not superior to sham controls for any of the disorders where evidence was available.[41]

The treatment was largely well-tolerated; serious adverse events such as seizure and treatment-emergent affective switch were rare (<0.5% for both); minor adverse effects included headache, facial pain, and scalp discomfort.[41] These conclusions are tempered by the small number of trials with high risk of bias and significant methodological heterogeneity. A recent trial has found that theta burst stimulation is safe and effective in patients with generalized anxiety disorder.[53] No Indian trials using rTMS were available in dementia, nicotine uses disorder, attention-deficit/hyperactivity disorder, and autism spectrum disorder.

Indian research on transcranial electrical stimulation

tES techniques have garnered significant attention in the Indian research landscape, with various studies exploring their efficacy across multiple neuropsychiatric conditions. The primary modalities investigated include tDCS, high-definition transcranial direct current stimulation (HD-tDCS), tACS, and tRNS.

Transcranial direct current stimulation in schizophrenia

Schizophrenia has received the maximum research attention in trials of tDCS in India. Fronto-temporal tDCS has shown significant efficacy in reducing auditory verbal hallucination severity, particularly in treatment-resistant cases.[54] These effects may be linked to improvements in key cognitive mechanisms, including auditory signal detection,[55] corollary discharge,[56] and source monitoring,[57] though the evidence is inconsistent on many of these areas. The findings suggest that tDCS may modulate specific neural circuits underlying hallucinations rather than exerting broad cortical effects.

Transcranial direct current stimulation in obsessive-compulsive disorder (OCD)

A recent randomized, double-blind, sham-controlled trial investigated the efficacy of tDCS targeting the pre-supplementary motor area (pre-SMA) in individuals with treatment-resistant OCD.[58] Authors found active tDCS was superior to sham stimulation, in reducing OCD symptom severity, suggesting a promising neuromodulator approach for cases unresponsive to conventional treatments.

Transcranial direct current stimulation in substance use disorder (SUD)

A randomized controlled trial using bifrontal tDCS demonstrated a significant reduction in craving among detoxified patients with alcohol use disorder, supporting its potential as an adjunctive treatment.[59] However, another sham-controlled trial found no benefits with adjunctive tDCS and emphasized the need to reconsider existing tDCS protocols.[60] Complementing these insights, a third study employing resting-state fMRI found that prefrontal tDCS augmented whole-brain network efficiency and inter-region connectivity in relevant AUD networks, indicating that its effects may extend beyond symptom relief to broader neuroplastic changes.[61] Together, these studies suggest that whereas tDCS holds promise for AUD treatment, future protocols should be individualized to optimize efficacy and target relevant neural circuitry.

Transcranial direct current stimulation for early augmentation in psychiatric disorders

A randomized controlled trial in adults with major depressive disorder found that bifrontal tDCS significantly improved depressive symptoms when used early alongside pharmacotherapy.[62] Parallel, adolescent-focused studies demonstrated that early tDCS augmentation was both safe and effective in reducing symptoms in OCD[63] and major depressive disorder (MDD),[64] in the short-term; these benefits attenuated significantly over time. All these trials reported good tolerability, with no serious adverse events, and meaningful clinical improvements over short-term follow-ups.

Indian research on HD-tDCS

In treatment-resistant depression, HD-tDCS priming of intermittent theta burst (iTBS) stimulation significantly improved depressive symptoms compared to sham HD-tDCS-primed iTBS stimulation, suggesting synergistic neuromodulator effects.[65] In schizophrenia, HD-tDCS targeting the prefrontal cortex showed promise in reducing negative symptoms in a pilot, randomized, sham-controlled study.[66] Additionally, among patients with opioid use disorder[67] undergoing early abstinence, HD-tDCS did not significantly alter key neurochemical markers—glutamate-glutamine and GABA levels—and were more effective in reducing withdrawal and craving symptoms. Collectively, these findings underscore the potential of HD-tDCS as a targeted and well-tolerated intervention with cross-diagnostic therapeutic potential.

Online transcranial direct current stimulation

A recent Indian proof-of-concept study investigated the effects of “online” HD-tDCS (“online” refers to combining a neuropsychological task with simultaneous administration of tDCS) on working memory in individuals with schizophrenia, compared to “offline” tDCS (isolated tDCS).[68] Authors did not find a significant between-group effect on working memory and other cognitive domains studied; they argued that a possible ceiling effect may have prevented detection of benefits when combining two treatments.

Indian research on transcranial direct current stimulation

A study investigated the differential effects of personalized theta and gamma tACS on resting-state EEG in healthy individuals.[69] Using a rigorous crossover design, authors found that theta- and gamma-frequency tACS produced distinct neuromodulator effects across temporal, spatial, and spectral EEG dimensions. Theta tACS enhanced frontal theta power, while gamma tACS entrained theta and beta bands in the parieto-occipital regions. These findings highlight the frequency-specific and regionally selective nature of tACS-induced brain modulation.

Collectively, the above studies highlight the therapeutic potential of tDCS and high-definition tDCS in treatment-resistant depression, schizophrenia, OCD, and substance use disorders, with benefits extending to symptom reduction, cognitive enhancement, and neurochemical modulation. Early augmentation in adolescents has also proven safe and effective. Additionally, tACS demonstrated frequency-specific EEG modulation. However, research gaps remain in long-term efficacy, optimal stimulation protocols, and individualized treatment approaches, necessitating larger, multi-site trials to validate and refine these interventions.

Other non-invasive brain stimulations techniques in the management of Psychiatric disorders (Centers offering services, types of other non-invasive brain stimulations facilities available, Indications for use, Indian research)

tRNS is a newer form of tES, where the alternating current stimulus is released with random amplitudes, and it produces a therapeutic effect by altering the pathological neuronal oscillations. It is being used for the treatment of psychiatric disorders in India. Two case reports[70,71] and a case series.[72] In all the three scenarios, tRNS was used for cognitive enhancement strategy in patients with cognitive impairment as a sequel of head injury, encephalitis, and hanging.

Transcutaneous auricular vagus nerve stimulation (taVNS) is available in few centers of India. Sarma et al.,[73] used it in the management of status epilepticus. In experimental animals, it has been studied in the chronically stressed rats[74,75] and the beneficial effects are studied in the metabolic parameters and level of stress. taVNS has also been used in the management of anxiety, stress, and sleep issues in different groups of populations (healthcare workers, teachers) in recent years.[76,77,78]

Transcranial Photobiomodulation is a newer form neuromodulation that uses laser rays of unique wave-length. In India, it is being used by the dental and dermatology disciplines for various therapeutic purposes.[79,80,81,82] One study that used intranasal photobiomodulation in anxiety reduction of pediatric dental patients.[83] However, this is largely under studied in the patients with psychiatric illness.

Researchers used transcutaneous electrical nerve stimulation (TENS) for trigeminal neuromodulation, in the treatment of trigeminal neuralgia.[23,84] However, its role in psychiatric disorders is not adequately evaluated in India.

Non-invasive brain stimulation in psychiatric disorders: Status in Maldives

After extensive searches on popular web databases such as Google and Bing, as well as research databases like PubMed, Scopus, and Google Scholar, we did not discover any information (as of March 2025) regarding the availability of NIBS techniques, including rTMS, tDCS, and ECT, in the Maldives.

Non-invasive brain stimulation in Psychiatric disorders: Status in Nepal

The neuromodulation in the form of ECT was started around half a century back in general hospital setting of Nepal.[85] It was used as a primary modality of treatment with high proportion of patient receiving ECT in the decades of 1970s and 1980s.[86] However, the other neuromodulation technique like rTMS and tDCS were started very recently within last 5 years.

rTMS in Nepal

Two public hospitals (Mental hospital Lagankhel and Patan academy of Health Sciences)[87,88] and few private setups have started rTMS in Nepal. However, there are no publication in scientific journals regarding the services. There has been one post graduate thesis completed and one ongoing in Mental Hospital Lagankhel in rTMS. One post graduate thesis on rTMS is ongoing in Patan Academy of Health Sciences. This information is on the basis information from the said institutions which have rTMS facility collected by the author till date. Deep rTMS has also been started in Nepal in Pokhara in a private setup.[89,90]

HD-tDCS in Nepal

This is available in a single center of Nepal in Mental Hospital Lagankhel that is a government setup.[88]

Non-invasive brain stimulation in Psychiatric disorders: Status in Pakistan

In Pakistan, NIBS remains in its nascent stages, with very limited clinical uptake to date. Although techniques like rTMS and tDCS have gained substantial international recognition, their application within psychiatric and neurorehabilitation services in Pakistan has been minimal. This is largely attributed to systemic limitations in infrastructure and service development within psychiatry, which have hindered the integration of emerging interventions like NIBS into mainstream clinical practice[91] and a notable gap in procedural training.[92] Additionally, much of the local research in this area is being led by neurologists, physiotherapists, and biomedical engineers rather than psychiatrists, which may partly explain the slow integration of NIBS into mainstream mental health care.

The availability of NIBS services in Pakistan remains critically limited, with only a handful of TMS machines available for a population exceeding 220 million, rendering access particularly difficult outside major urban centers.[91] However, a few centers in metropolitan cities have begun to offer rTMS and tDCS. For instance, in Karachi, Transformation Wellness Clinics provide FDA and CE approved rTMS services, delivered by a multidisciplinary team that includes UK and US trained professionals. Additionally, The Sleep Centre has been noted to provide tDCS, thereby broadening the scope of neuromodulation options. Moving north, in Rawalpindi, the Pakistan Institute of Mental Health integrated rTMS into psychiatric care in March 2022, offering treatment for individuals with psychiatric disorders. Before this, rTMS services had already been established at NARI Hospital in Lahore. Significantly, in Gujranwala, Professor Saqib Bajwa was the first to introduce rTMS in a public-sector setting, marking an important step toward wider accessibility. More recently, Ayub Teaching Hospital in Abbottabad launched its rTMS service in February 2024 under the leadership of Professor Dr. Aftab Alam Khan. The service primarily targets depression, OCD, and anxiety, and has treated over 100 patients to date. Nonetheless, affordability remains a key challenge, as each session costs PKR 1,500, with full treatment protocols often requiring up to 40 sessions.

An expanding body of evidence supports the use of rTMS in the treatment of depression and obsessive-compulsive disorder,[91] while tDCS has demonstrated utility in stroke rehabilitation,[93,94] and acoustic stimulation is emerging as a potential intervention for post-concussion syndrome.[95] Notably, researchers at Liaquat University of Medical and Health Sciences in Jamshoro have developed a low-cost tDCS prototype, with the aim of enhancing accessibility to neuromodulation technologies in low-resource settings.[96] In parallel, the Neurotransmission Cognitive Theory proposes a novel approach using mechanical vibration-based stimulation applied to nerve points to aid neurorehabilitation.[97] Preliminary use in conditions like dysarthria and cerebral palsy shows promise, though the approach remains hypothetical and requires further clinical validation.

Despite increasing global acceptance of NIBS, several structural and systemic barriers continue to hinder its widespread use in Pakistan. These include high treatment costs limited public and professional awareness, and the absence of clear regulatory frameworks to guide safe and effective implementation.[91,93,96] A recent study involving speech-language pathologists and neurologists revealed that while NIBS is broadly recognized as a safe and promising intervention, formal training in its application remains rare.[98] This training gap is even more pronounced among psychiatrists, who often remain untrained in rTMS, restricting its clinical uptake as a viable alternative to ECT. Although ECT continues to be a more cost-effective option for treating severe depression, rTMS offers a significant advantage in terms of cognitive safety, particularly about preserving memory function.[92]

Given the current scarcity of NIBS facilities across the country, there is an urgent need to expand and integrate these interventions into public-sector healthcare settings to enhance accessibility and equity in mental health care provision.[91] For meaningful clinical adoption, this expansion must be accompanied by the development of standardized national guidelines, structured training pathways, and sustainable funding mechanisms.[95,96,98] Yet, the structure of consultant roles within the public sector often makes it difficult for psychiatrists to directly oversee or provide rTMS services. The gap between such regulatory clarity abroad and the fragmented implementation locally highlights the need for stronger leadership and governance within Pakistan. In this regard, the Pakistan Psychiatric Society has a critical role to play, not only in formulating practice standards, but also in investing in capacity-building and facilitating the integration of NIBS into mainstream psychiatric care through sustained efforts in research, policy, and service development.

Non-invasive brain stimulation in Psychiatric disorders: Status in Sri Lanka

After conducting a thorough search across various platforms, including popular search engines like Google and Bing and academic databases such as PubMed, Scopus, and Google Scholar, we discovered a lack of information regarding the availability of noninvasive brain stimulation techniques in Sri Lanka. Specifically, techniques like rTMS and tDCS appear to be unavailable in the country.

As of March 2025, the only established neuromodulation treatment available for the management of psychiatric disorders in Sri Lanka is ECT. This limitation highlights the need for greater access to innovative treatment options for individuals suffering from mental health conditions in Sri Lanka. Further research and investment in mental health technologies could potentially enhance treatment options available for patients in Sri Lanka.

RESEARCH GAPS AND WAYS FORWARD

As several South Asian countries (Afghanistan, Bhutan, the Maldives, and Sri Lanka) lack facilities for NIBS aside from ECT, the existing research is confined to only a few countries [Table 2]. The timeline of the introduction of various neuromodulation facilities in South Asia is summarized in the Figure 1. Bangladesh and Pakistan have limited settings for NIBS, and there is a scarcity of published research from these two nations. In India, NIBS modalities are expanding rapidly, with several studies on NIBS conducted in India over the past two decades. Post-doctoral fellowship programs at NIBS have been initiated in recent years in some of the premier institutes in India. This article majorly relied on the published research available, though we have taken the information available in the institutional websites and personal accounts of the academicians of the representative countries. It can be a limitation of this article. A survey of the mental health professionals regarding NIBS facilities may give a better insight to the practice pattern of NIBS in South Asia.

Table 2.

Availability of non-invasive brain stimulation (NIBS) and other neuromodulation techniques in South Asian Countries (as of March 2025)

Country	rTMS	tDCS/HD-tDCS/tACS	taVNS/VNS	ECT	Remarks
Afghanistan	–	–	–	+	ECT is the only available neuromodulation option. No other NIBS techniques reported.
Bangladesh	+ (Private)	–	+ (Available at INDR)	+	rTMS in private setups (Dhaka); VNS for autism available at INDR; No information on other NIBS techniques.
Bhutan	–	–	–	+	Only ECT available; No information on other NIBS techniques.
India	+ (Widely studied)	+ (tDCS, HD-tDCS, tACS)	+	+	Advanced NIBS research; multiple devices (Magstim, Soterix, etc.); diverse psychiatric applications.
Maldives	–	–	–	–	No available data on any neuromodulation technique.
Nepal	+ (Public & Private)	+ (HD-tDCS)	–	+	rTMS in public & private setups; HD-tDCS at Mental Hospital Lagankhel. No other NIBS services reported.
Sri Lanka	–	–	–	+	Only ECT available No other NIBS services reported.
Pakistan	+ (Urban centers)	+ (Limited use; tDCS, prototypes)	–	+	rTMS and tDCS available in few centers (Karachi, Lahore, Rawalpindi, Abbottabad) No other NIBS services reported.

+=Present, –=Absent/No data

Figure 1.

The timeline of the introduction of neuromodulation facilities in South Asia

CONCLUSION

Non-invasive neuromodulation techniques are gaining recognition as effective interventions for addressing a variety of psychiatric disorders. A significant recent development or a surge in publications that necessitates an update. In South Asia, particularly in India, there has been a notable increase in the utilization of these innovative methods. Among the most widely used techniques are rTMS and tDCS, both of which offer promising outcomes with minimal side effects. Over the past decade, the research surrounding non-invasive neuromodulation has significantly expanded, yet it remains largely concentrated in India. This growing body of research highlights the potential of these techniques to revolutionize the treatment landscape for psychiatric conditions, providing new hope for patients seeking alternatives to traditional therapies. As interest continues to grow on neuromodulation, the future appears promising for the integration of these advanced modalities into clinical practice.

Declaration regarding the use of generative AI

None used for generation of text. We used Grammarly to improve the language and fix the grammatical errors.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.