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

Table 2

Summary of the studies in HRV, RSA, and HR biofeedback.

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)

Karavidas et al. [80]

Y

C, P1

Y

—

—

—

—

—

Y

Y

Y

—

—

Caldwell and Steffen [57] (women)

Y

P1

Y

Y

Y

Y

Y

—

Y

Y

Y

Y

—

Breach [81]

Y

C, P1, P2

Y

Y

—

Y

—

—

Y

Y

—

—

—

Lin et al. [82] (sleep problems)

Y

P1

Y

Y

Y

—

Y

—

Y

Y

Y

Y

—

Depressive disorders other than MDD

Siepmann et al. [83]

Y

P1

Y

—

—

—

—

—

Y

Y

Y

—

—

Bunthumporn [85] (elderly)

Y

P2

Y

Y

—

—

Y

Y

Y

Y

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); C: clinical outcome measure; P1: well-established subjective test of depression; P2: other subjective test of depression.