Quantity of Research Available
The literature search yielded 175 citations. No additional studies were identified by searching the grey literature. After screening of abstracts, 19 potentially relevant studies were selected for full-text review. Among these 19 studies, one was excluded because the full text article could not be retrieved,17 and 15 did not meet the selection criteria.
Three studies18–20 were included in the review: one on PTSD18 and two on depression.19,20 One was a systematic review,18 one was a randomized controlled trial (RCT),19 and one was a non-RCT (cohort study), in which patients from two long-term care facilities were assigned to either biofeedback therapy or usual care.20 The RCT and non-RCT were published dissertations; however they were not peer-reviewed. No relevant evidence-based guidelines were identified. The PRISMA flowchart in Appendix 1 details the process of the study selection.
Summary of Study Characteristics
Characteristics of the included systematic review and RCTs are summarized below and details are provided in Appendix 2.
Systematic reviews
Wahbeh and colleagues conducted a systematic review to evaluate the evidence of complementary and alternative medicine including biofeedback for PTSD (Appendix 2).18 Multiple databases were searched from 1950 to March 2013. There was no restriction on language. Controlled and uncontrolled studies enrolling at least five patients and reporting at least one measure assessing PTSD symptoms were eligible for this review. The quality of the included studies was assessed using the Cochrane Risk of Bias Tool (for RCTs only) and the Quality Assessment Tool (for RCTs and non-RCTs). The level of scientific evidence was graded for each treatment modality for PTSD to reflect the strength of available scientific data for or against the use of each therapy: A = strong scientific evidence; B = good scientific evidence; C = unclear or conflicting scientific evidence; D = fair negative scientific evidence; F = strong negative evidence; L = lack of evidence. These grades were determined based on the numbers, the design, the quality, as well as the results of the included studies. For instance, level A was assigned when there was statistically significant evidence of benefit from more than two properly conducted RCTs, or from one properly conducted RCT plus one properly conducted meta-analysis, or from multiple RCTs with a clear majority of the properly conducted trials showing statistically significant evidence of benefit in addition to supporting evidence in basic science, animal studies or theory. Level F was assigned when statistically significant negative evidence from more than one properly conducted RCT. A total of 33 studies (17 RCTs, 4 non-RCTs, 9 pre-post designs and 3 crossover interventions) were included in this review. Among them, four enrolled patients treated with biofeedback (heart rate variability [HRV] biofeedback, pain-focused cognitive behavioral biofeedback, and respiratory sinus arrhythmia biofeedback therapy). The number of patients involved in the four studies on biofeedback ranged from 13 to 50. The number of received treatment sessions ranged from six to 28 and the duration of each session ranged from 20 minutes to 90 minutes. The primary outcomes of included studies were changes in symptoms of PTSD, based on PTSD Checklist-Military Version (PCL-M), Clinician-Administered PTSD Scale (CAPS), Posttraumatic Diagnostic Scale (PDS), and Posttraumatic Stress-Total scale of the Detailed Assessment of Posttraumatic States (PTS-T).
Randomized and non-randomized controlled trials
The RCT by Breach was conducted in the US,19 and the non-RCT by Bunthumporn was conducted in Thailand.20 Patients in both studies received 10 sessions of HRV biofeedback therapy, for 20 minutes per session in the Breach study and 30 minutes per session in the Bunthumporn study. Detailed characteristics of the included studies are summarized in Appendix 2.
Population
Patients in these two studies were diagnosed with depression.19,20 All patients were adults aged 18 years old and older. The Thai study recruited senior patients (mean age of 76 years old) living in assisted facilities.
Interventions and comparators
HRV biofeedback was investigated in both studies. It was compared to a sham control in the RCT, and compared to usual treatment such as morning exercise and social/recreational activities in the non-RCT.19,20
Outcomes
The primary outcomes of included studies were changes in symptoms of depression based on Hamilton Depression Inventory (HAM-D), Beck Depression Inventory (BDI), Thai Geriatric Depression Scale (TGDS), and Depressive Cognition Scale (DCS).
Summary of Critical Appraisal
A summary of the critical appraisal conducted for selected studies can be found in Appendix 3.
In the systematic review by Wahbeh et al., a comprehensive literature search was performed with no restrictions on language or study design. Two reviewers performed study selection independently. One single reviewer extracted data and a second reviewer verified the accuracy and completeness of data extraction. The methodological quality of the selected studies was examined by two reviewers independently. Level of evidence was graded to assist in drawing conclusions. A meta-analysis was not conducted due to the high degree of heterogeneity of the included studies. The quality of this systematic review was compromised by insufficient data reporting, limited number of included biofeedback studies, and small number of enrolled patients in the included individual studies. The minimal clinically important differences (MCIDs) were not reported; therefore the clinical relevance of the evidence was undetermined. The authors indicated that publication bias was present when studies with positive results were more frequently published compared to those with negative results, although the method used to detect publication bias was not described.
The RCT by Breach enrolled 11 patients. The author indicated that a restricted randomization procedure was adopted for treatment allocation without providing more details. The study investigators who entered and edited the data were not blinded to patient’s condition; however, it is unclear whether the outcome assessors of this study were blinded to patient’s condition and treatment assignment. Evidence from this study was inconclusive, potentially due to the small sample size, though a power calculation to determine the number of participants required to detect significant differences between treatment groups was not reported. Patients in this RCT may not reflect the broader population who would be typically seen in practice. The author stated that 45% of the participants in this study had severe or very severe depression, while 9% of the participants had mild depression.
The non-RCT was conducted in Thailand. In order to determine the sufficient number of patients needed in the study, three different statistical tests were performed and eventually the highest sample size calculated from one of the tests was used for the study. A convenient sample instead of consecutive sample was gathered in this study, therefore the study results may not be generalized to the entire patient population. The employed assessment scales had to be translated from English to Thai for the patients to complete. Therefore, the accuracy of the translation was uncertain. Generalizability of the study results to a Canadian population was unclear.
Summary of Findings
Main study findings and authors’ conclusions can be found in Appendix 4.
- 1.
What is the clinical evidence for the benefits and harms of neurofeedback provided by a health professional for post-traumatic stress disorder, generalized anxiety disorder, or depression?
No studies on the clinical evidence regarding the benefits and harms of neurofeedback for post-traumatic stress disorder, generalized anxiety disorder, or depression were identified.
- 2.
What is the clinical evidence for the benefits and harms of biofeedback provided by a health professional for post-traumatic stress disorder, generalized anxiety disorder, or depression?
In the Wahbeh review, four studies examined the clinical effectiveness of biofeedback in patients with PTSD.18 In three out of four studies, the results showed that the symptoms of PTSD were significantly reduced after biofeedback therapy (20 to 30 minutes per session, six to 28 sessions in total) or usual treatment (not specified in the review), but the difference between two treatment groups was not statistically significant. The fourth study had a pre-post study design and recruited 13 refugees with PTSD, chronic pain and experience of torture or war. Results from this study indicated no significant changes in PTSD symptoms were observed over time
A non-RCT examined the effect of HRV biofeedback on 100 senior Thai patients with depression.20 Participants were treated with five weeks of HRV biofeedback therapy (twice a week and 30 minutes per session) or with usual treatment. Depressive symptoms were assessed using the Thai version of assessment scales specific for depression. At the end of the treatment, statistically significant reductions in depressive cognition and depressive symptoms scores were observed in the biofeedback therapy group, but not in the control group. Due to the absence of MCIDs, assessment of the clinical importance of the between-group differences could not be done. The authors indicated that the study suggested a beneficial effect of biofeedback on depressive symptoms in senior patients.
- 3.
What is the clinical evidence regarding home use of biofeedback equipment for post-traumatic stress disorder, generalized anxiety disorder, or depression?
An RCT examined the effect of HRV biofeedback on 11 adults with depression.19 Participants were treated with 10 weekly HRV biofeedback sessions or with sham biofeedback control. In the biofeedback group, patients firstly received 4 weeks training on HRV biofeedback, and the treatment continued at home thereafter. Reductions in depressive symptoms were observed in both treatment and control groups after 10-week HRV biofeedback therapy or sham therapy. The between-group differences for the outcome measures did not reach statistical significance evaluated by HAM-D and BDI-II.
- 4.
What are the evidence-based guidelines regarding the use of neurofeedback or biofeedback for the treatment of post-traumatic stress disorder, generalized anxiety disorder, or depression?
The literature search did not identify any evidence-based guideline regarding the use of neurofeedback or biofeedback for the treatment of post-traumatic stress disorder, generalized anxiety disorder, or depression.
Limitations
In this update, the literature search did not identify clinical evidence regarding the effectiveness and safety of neurofeedback therapy. There were no studies identified for patients with generalized anxiety disorder. Due to the limited number of biofeedback studies identified (n = 3) and the poor quality of the clinical trials, it is difficult to draw definitive conclusions regarding the clinical effectiveness and safety of biofeedback on PTSD and depression. The two clinical trials were short-term studies with preliminary analyses on small number of participants, which limit the generalizability of the findings to the target populations. Even though HRV biofeedback was evaluated in both studies, various HRV biofeedback techniques were employed (different equipment and treatment frequency/duration) and the study results were inconsistent in terms of statistical significance of the between-group difference.19,20 In addition, the non-RCT used the Thai version clinical scales in outcome assessment. No relevant evidence-based guidelines were found.
