Table 3 Characteristics of studies reviewed in the current applications of non-invasive brain stimulation in neuropsychiatric disorders

Depression and mood disorders

Case series (Li and colleagues 2014) [23]

9 patients

Accelerated theta burst rTMS

Significant clinical improvement in depression symptoms as early as day 8

Small sample size, lack of control arm

Case series (Mayberg and colleagues 2017) [24]

6 individuals

Chronic stimulation of white matter tract near subgenual cingulate gyrus

Durable remission of depression in 4 out of 6 individuals

Small sample size

Randomised controlled trial (Tomlinson and colleagues 2017) [25]

Patients with unipolar depression

tDCS versus escitalopram

Superiority of tDCS over placebo in treating unipolar depression

Did not achieve non-inferiority to escitalopram

Factorial, double-blind, placebo-controlled trial (Brunoni and colleagues 2013) [26]

120 patients

tDCS alone, tDCS + sertraline, sertraline alone

Combination therapy outperformed tDCS alone, tDCS alone superior to sertraline alone in improving certain symptoms

Relatively low dose of sertraline used in the study

Schizophrenia and psychotic disorders

Randomised sham-controlled study (Bation and colleagues 2021) [28]

Individuals with treatment-resistant negative symptoms of schizophrenia

Intermittent theta burst rTMS (iTBS)

Significant reduction in negative symptoms compared to sham, sustained improvement after 6 months

Need for further large-scale sham-controlled studies to validate results

Open-label retrospective study (Brunelin and colleagues 2022) [29]

Patients with treatment-resistant auditory hallucinations

rTMS

Significant reduction in auditory hallucinations, even in clozapine-resistant patients

Need for large-scale randomised sham-controlled studies to confirm findings

Randomised controlled trial (Valiengo and colleagues 2020) [30]

Patients with negative symptoms of schizophrenia

tDCS

Active tDCS group showed significant improvement compared to sham group, sustained effects during follow-up

Well-tolerated, transient burning feeling as a side effect

Anxiety disorders and PTSD

Double-blind, placebo-controlled phase II trial (Vergallito and colleagues 2022) [32]

30 patients with PTSD

Active 20 Hz rTMS of right DLPFC, active 20 Hz rTMS of left DLPFC, sham rTMS

Both active rTMS groups significantly reduced PTSD symptoms, with sustained benefits at three-month follow-up

Need for larger studies to confirm results and establish efficacy

Pilot randomised, double-blind, sham-controlled study (Diefenbach and colleagues 2016) [33]

Patients with generalised anxiety disorder (GAD)

rTMS

Active rTMS groups showed higher response and remission rates compared to sham group

Preliminary findings, need for larger studies with rigorous designs

Randomised, single-blind, pharmacotherapy and sham-controlled clinical study (Movahed and colleagues 2018) [34]

Patients with GAD

tDCS

Active tDCS treatments beneficial in reducing anxiety, worry, and depressive symptoms

tDCS more effective than medication in reducing depressive symptoms, less successful in alleviating worry symptoms

Cognitive disorders and neurodegenerative diseases

Randomised, double-blind, sham-controlled experiment (Benussi and colleagues 2020) [36]

Frontotemporal dementia (FTD) patients

tDCS

tDCS increased intracortical connectivity and improved clinical ratings and behavioural abnormalities

Sham stimulation did not yield significant benefits

Randomised, double-blind, sham-controlled trial (Wu and colleagues 2015) [37]

Alzheimer's disease (AD) patients with behavioural and psychiatric symptoms

High-frequency rTMS

Combination of antipsychotic medication with high-frequency rTMS led to significant improvements in symptoms

Need for further research to confirm efficacy and establish optimal protocols

Other neuropsychiatric conditions

Quasi-experimental study (Akbarzadeh and colleagues 2021) [38]

Individuals with OCD

rTMS

rTMS significantly reduced OCD symptoms and decreased beta wave activity in parietal and occipital regions

Need for controlled studies to validate findings and establish efficacy