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

Table 1

Description of requirements of each level of evidence. Summarized from [11].

Level of evidence	Data supporting clinical efficacy of protocol
(1) Not empirically supported	Anecdotal reports, case studies
(2) Possibly efficacious	One study of sufficient statistical power with well-identified outcome measures; randomization is optional
(3) Probably efficacious	Multiple observational, clinical, waitlist controlled studies; within- and intrasubject replication studies
(4) Efficacious	Two or more independent randomized studies demonstrating superiority of biofeedback to no treatment, alternative treatment or placebo, or noninferiority to treatment as usual (if sufficient statistical power to detect moderate differences is achieved); clearly defined and valid inclusion criteria, treatment procedures, outcome measures, and data analysis
(5) Efficacious and specific	Two or more independent randomized studies demonstrating superiority of biofeedback to sham therapy or alternative treatment