. 2023 Jul 6;21:eRW0253. doi: 10.31744/einstein_journal/2023RW0253

Table 1. Characteristics of the studies included in the systematic review.

Study	NF type	Methodology	Depression scales	Total number of sessions	Results
Mehler et al.⁽⁴⁾	fMRI-NF	Any mental strategy NFE: imagery of positive stimuli NFS: imagery of scenes	HDRS, HADS	5	Significant improvement up to 25% upregulation of emotion areas and 50% upregulation of a control region activated by visual scenes
Tsuchiyagaito et al.⁽⁵⁾	rtfMRI-NF	Upregulated LA activity with kynurenine measured using two task block regressors, “happy” and “count”	MADRS	2	Thirteen participants exhibited a ≥25% reduction in the MADRS score
Cheon et al.⁽⁶⁾	Asymmetry rotocol	Training of the left hemisphere with beta waves at F3 and with alpha/theta waves at Pz	HAM-D, HAM-A, BDI-II, BAI	16 to 24	Significant improvement in HAM-D scores
Chen et al.⁽⁷⁾	Asymmetry protocol	Training with delta, theta, alpha, and low and high beta waves at P3 and P4	BDI-II, BAI	10	Significant improvement of cognitive depression but not somatic depression
Wang et al.⁽¹⁴⁾	Asymmetry protocol	ALAY protocol, down-training of the alpha power at F3, and up-training of alpha power at F4	BDI-II, BAI	6	57.14% of the subjects did not respond to the intervention
Choi et al.⁽¹⁵⁾	Asymmetry protocol	EEG from F3 and F4 in a trial with classical music where the participants had to keep the sound on and try to raise its volume	HAM-D, BDI-II	50% of the participants with depression showed significant improvement	50% of the participants with depression showed significant improvement
Zotev et al.⁽¹⁶⁾	rtfMRI-EEG-NF	Real-time display screen for happy memories, with task runs and simultaneously frontal EEG in the upper alpha band	HDRS, HARS, MADRS, SHAPS, HAS, TAS, POMS, STAI, VAS	2	Significant improvement by VAS, POMS, HDRS, and SHAPS
Zotev et al.⁽¹⁷⁾	rtfMRI-EEG-NF	Real-time GUI display screen for happy memories with task runs alpha and high-beta EEG for F3 and F4	MADRS, POMS, STAI, SHAPS	Differences between the control and experimental groups did not reach significance	The control and experimental group were not significantly different
Takamura et al.⁽¹⁸⁾	rtfMRI-NF	A run of rest block (gray) and up-regulation block (green) that the participants had to raise the signal in the green as compared to the gray signal, target ROI	BDI-II, HDRS, RRQ	5	Significant improvement by RRQ
Young et al.⁽¹⁹⁾	rtfMRI-NF	Real-time display screen to recall happy autobiographical memories with task runs, target ROI	MADRS, POMS, VAS, STAI	1	Significant improvement in the scales related to mood effects
Young et al.⁽²⁰⁾	rtfMRI-NF	Patients had to retrieve positive memories while attempting to increase the hemodynamic activity in the assigned region. With task runs.	MADRS, BDI-II, SHAPS, HAM-D, HAM-A, BDI-II, SHPS	2	The responder groups exhibited significant improvement
Schneider et al.⁽²¹⁾	SCP-NF	Trial of visual feedback of SCP where the assignment of trial type (negative or positive slow potential) was discriminated by the stimuli	HAM-D, GAS, BPRS	20	Minimal correlation with depression scales
Liu⁽²²⁾	Asymmetry protocol	Alpha-beta protocol (suppress alpha wave and amplified beta wave) of the left hemisphere at F3 and two other electrodes on the eardrum	BDI-II	9	No significant improvement

fMRI-NF: Functional magnetic resonance imaging neurofeedback; HDRS/HAM-D: Hamilton Depression Rating Scale; HADS/HAS: Hospital Anxiety and Depression Scale; MADRS: Montgomery–Asberg Depression Rating Scale; HAM-A: Hamilton Anxiety Rating Scale; BDI-II: Beck Depression Inventory; BAI: Beck Anxiety Inventory; SCP-NF: Slow cortical potential Neurofeedback; GAS: Goal Attainment Scaling; BPRS: Brief Psychiatric Rating Scale; POMS: Profile of Mood States; VAS: Visual Analogue Scale; STAI: State-Trait Anxiety Inventory; RRQ: Rumination-Reflection Questionnaire; EEG: electroencephalography; SHAPS: Snaith–Hamilton Pleasure Scale; TAS: Toronto Alexithymia Scale; GUI: graphical user interface; ROI: region of interest.