Table 1.

Summary of characteristics of published original research in the field of home-based tDCS for the treatment of depression

Author, year	Study type, disorder (primary)	Number of participants, age, gender	Conditions Electrode positioning, intensity, duration, number of stimulations	Operator, mode of supervision	Adverse effects, feasibility	Outcome parameters, results	Strengths (S) and weakness (W)	Quality measures during stimulation series A = adherence control Q = quality of stimulation S = safety assessment T = technical monitoring V = regular visits
Alonzo et al. [26]	Open label pilot trial, major depressive episode of a unipolar or bipolar depression, at least 4 weeks	N = 34, group 1: N = 15, 6 female, 48.64 ± 11.56 years, group 2: N = 20, 7 female, 46.10 ± 13.55 years	Single condition, active: anode F3, cathode F8, 2 mA, 30 min, 20 or 28 sessions in 4 weeks and taper phase of 4 sessions in 4 weeks	Standardized training and checklist in clinic (1 session), Self-administered by patients, remotely observed by research staff via videolink (as needed)	No SAEs Most common side effects: tingling, burning, redness Drop-outs: 2: inability to master set-up, missed sessions. 93% of scheduled sessions completed	Changes from baseline to 1-month follow-up in: MADRS QIDS-SR Q-LES-Q-SF Significant main effect of time in all scales, no effect of session frequency	S: standardized procedures, regular visits and supervision W: no sham condition	A = yes Q = yes S = yes T = yes – electrode contact quality V = yes
Borrione et al. [27]	Case series, open label, combination of home-based tDCS with App based psychological intervention, MDD	N = 5, 4 female, 41.6 ± 9.8 years	Single condition, active + app-based intervention: one-size-fits-all cap, prefrontal, anode left, cathode right, 2 mA, 30 min, 21 sessions in 6 weeks	supervised training, self-administered, remote access to study team in case of any questions or complications	No SAEs All 5 subjects finished the protocol, no drop-outs	Changes from baseline to week 6 in: MADRS, Ham-D-17, BDI-II. 4 treatment responders, 3 remission	S: + app-based intervention. W: no control group, only 5 patients, one-size-fits-all cap	A, Q, S, T in supplementary material, not available. V = yes (baseline, week 2, 3, 4, 6)
Cappon et al. [22]	Open label pilot trial on study companion-administered tDCS at home in older patients with MDD	N = 5 (3), two withdrew in the first week, 0 female; 46–72 years	Single condition, active, multichannel tDCS montage with Stimweaver algorithm, F3 (anode), FZ, FC5, and FP1 (cathodes), 1,75 mA max. current, 30 min, 37 sessions in 8 weeks	Study companion-administered after standardized training programme, remote practice sessions, on-demand remote assistance	No SAEs, most frequently reported tingling, itching, sleepiness, scalp redness. 2 drop-outs: medical conditions unrelated to treatment. Of remained patients only one session was missed	Changes from baseline to week 4, 8 and 12 (follow-up) in: MADRS, QIDS-SR16, HDRS, BDI-II. MADRS decreased in all 3 completers (average decrease: 59% baseline to 1-month follow-up), same trend for the other scores	S: new training programme, electrode montage multichannel. W: only 3 patients completed, ratings via phone, no control group	A = yes Q = yes S = yes T = no V = no
Mota et al. [31]	Randomized, double-blind, sham-controlled clinical trial for home-based tDCS in depression in temporal lobe epilepsy	N = 26 13 active, 12 female 53.38 ± 14.45 years, 12 sham, 10 female 55.76 ± 7.68 years	Active and sham condition, prefrontal: anode left, cathode right, 2 mA, sham: no current, 20 min, 20 sessions in 4 weeks home-based, then 3 sessions in 3 weeks in-clinic	Self-administered after training by a clinician and with instructional video	7 moderate or severe AEs in active, 3 in sham group: headache, most common side effects were tingling, itching, burning, headache, somnolence, moodswings. Drop-out: 1 (active): pain, burning discomfort. 2 (sham): travel, loss of interest	Changes from baseline to week 2,4, 8 in the BDI-II (primary Outcome), QOLIE-31 and HAM-A score (secondary Outcome), improvement over time but no group difference	S: active and sham, monitoring of technical parameters. W: different groups of medications	A = yes Q = yes S = yes T = yes V = yes
Sobral et al. [28]	Case series, open label, combination of home-based tDCS with App based psychological intervention, MDD and/or comorbidities	N = 7, 4 female, 26–51 years old;	Single condition, active + app-based intervention: one-size-fits-all cap, prefrontal, anode left, cathode right, 2 mA, 30 min, 18 or 21 sessions in 6 weeks	Supervised training, self-administered by patients, clinical progress monitoring in person and remotely using Zoom	No SAEs, most common AEs: scalp irritation, tingling, itching, and burning sensation. Adherence and acceptability overall high (ACCEPT-tDCS scores), 2 patients missed > 50% tDCS sessions (personal challenges), 1 drop-out (compliance)	Changes from baseline to week 6 in: MADRS-Self rating and BDI-II, STAI-Trait clinical improvement in MADRS-S in 5 patients and in STAI-Y2 5 patients	S: combination with app-based intervention W: 2 patients initiated CBT at same time as study, no control group	A = yes Q = no S = yes T = no V = yes
Woodham et al. [30]	Open label, single-arm study of home-based tDCS in MDD	N = 26, 19 female, 40.9 ±  14.2 years	Single condition, active tDCS, F3 anode, F4 cathode, 2 mA, 30 min, 21 sessions in 6 weeks	Self-administered, research team member was present in person or by real-time video call at each session	No SAEs, most common side effects were skin redness, tingling, itching, mild burning sensation, headache. Acceptability rated high, drop-outs: 3 (broken device, physical health, personal reasons), 92,8% completed 6 weeks of treatment	Changes from baseline to week 6 and after 3 and 6 months follow-up in: HAMD. Response in 22 (20) participants, clinical remission in 21 (18) at week 6 (after 6 months)	S: 26 patients included, long follow-up phase, Acceptability questionnaire. W: no control group	A = yes Q = no S = yes T = no V = yes
Le et al. [29]	Case series, retrospectively examined clinical data, MDD	N = 16, no further information, only abstract available	Single condition, active tDCS, different protocols, up to 2 years of treatment, at least 6 weeks	Self-administered at home	No SAEs, 2 patients withdrawn because of blurred vision or exacerbation of tinnitus	5 patients responded to acute tDCS within 6 weeks, 9 patients who received tDCS for more than 12 weeks maintained improvements over several months	S: long observation period W: no control group, active group very inhomogenious	No further information
Oh et al. [32]	Randomized, single-blind, sham-controlled clinical trial, parallel group, MDD, home-administered tDCS + Escitalopram 5–20 mg/d	N = 58, 29 (20) active, 29 (25) sham, 9 drop-outs in active, 4 in sham group, Active: 10 female, 29.7 ± 11.6 years, sham: 10 female 28.5 ± 11.0 years	Active and sham condition, anode F3, cathode F4, active: 2 mA, sham: no current, 30 min, 30 sessions in 6 weeks	Self-administered at home, instruction once by a research nurse, online manuals	2 skin burns (forehead) Drop-outs: 13 (9 active: 2 burns, 7 poor treatment compliance; 4 sham: 4 poor treatment compliance)	Changes from baseline to week 6 in: MADRS, HAM-D, BDI. Improvement in all scales over time, BDI score decrease was significantly different between the active and sham tDCS groups	S: active and sham condition, regular visits. W: single-blinded design	A = yes Q = no S = yes T = yes (current density) V = yes
Lee et al. [33]	Randomized, double-blind, sham-controlled clinical trial for home-based tDCS in bipolar depression	N = 64, 47 female, 33.4 ± 12.6 years	Active and sham condition, anode F3, cathode F4, active: 2 mA, sham: no current, 30 min, up to 42 sessions in 6 weeks	Instructions, self-administered at home, video training, on-demand video or voice calls	No SAE, most common side effects were headache, skin redness, tingling. Drop-outs: 26 (13 active: 8 poor compliance < 60% scheduled sessions, 3 withdrawals, 2 of them due to AE; 10 sham: 7 compliance < 60% of scheduled sessions, 1 AE, 1 patients request, 1 non-compliance)	Changes from baseline to week 2,4, 6 in the HDRS-score between groups over time time-group interaction for the HDRS-17 were not statistically significant	S: active and sham condition, regular visits. W: no follow-up	A = yes Q = no S = yes, only every 2 weeks T = no V = yes

MADRS Montgomery Asberg Depression Rating Scale, QIDS-SR Quick Inventory of Depressive Symptomatology self-report, QLESQ-SF Quality of Life Enjoyment and Satisfaction Questionnaire–Short Form