The Current Evidence Levels for Biofeedback and Neurofeedback Interventions in Treating Depression: A Narrative Review

Table 3

Summary of the studies in frontal alpha asymmetry neurofeedback.

Article	Sample	Demonstrates efficacy	Outcome measures	Statistical power	Control group	Multiple studies	Randomization	Superior to NT, PLA, or AT	Noninferior to TAU	Inclusion criteria	Treatment procedures	Data analysis	2+ independent studies	Superiority to PLA or AT
Required for level		1	2	2	3	3	4	4		4	4	4	4	5
Major depressive disorder (MDD)
Peeters et al. [38]		Y	P2	Y	—	—	—	—	—	Y	Y	Y	—	—
Wang et al. [112]		Y	P1	Y	Y	—	—	Y	—	Y	Y	Y	—	—
Cheon et al. [113] (F3 β↑, Pz α↓θ↑)		Y	C, P1	Y	—	—	—	—	—	Y	Y	Y	—	—
Depressive disorders other than MDD
Choi et al. [114]		Y	C, P1, P2	Y	Y	—	Y	Y	—	Y	Y	Y	—	Y/N
Ramirez et al. [115] (Emotiv A↑, β/α↑, elderly)		Y/N	P1	—	—	—	—	—	—	—	Y	—	—	—

EG: sample size of the experimental group; CG: sample size of the control group; NT: no treatment; PLA: placebo intervention; AT: alternative treatment; TAU: treatment as usual; Y: yes (criterion fulfilled); Y/N: yes/no (criterion partly fulfilled); C: clinical outcome measure; P1: well-established subjective test of depression; P2: other subjective test of depression; A: frontal alpha asymmetry; α, β, θ: EEG frequency bands; ↑: upregulation; ↓: downregulation.