May 09 2008

Brainwave Entrainment – A Response from Transparent Corp.

Earlier this week I wrote about the marketing of devices for brainwave entrainment for therapeutic use, concluding that these devices and the claims made for them are pseudoscientific. In response to my blog post I received the following e-mail:

Dear Dr. Novella,

I am the director of research at Transparent Corporation, which is the developer of Neuro-Programmer, and was disappointed to read your blog entitled “Brainwave Entrainment and Pseudoscience”.

I fully acknowledge that peer reviewed research on Brainwave entrainment is hard to locate, and it is one of the biggest hindrances to the field. The greatest barrier to finding this research is the lack of consistency in terminology used to describe brainwave entrainment. In fact, the term “brainwave entrainment” appears to have been invented by those in the industry, rather than those who have published on the subject. In the last year, I wrote an article entitled “A comprehensive review of the psychological effects of brainwave entrainment” which has been accepted in Alternative Therapies in Health and Medicine and I’ve been told will be published this summer. I’ve attached a copy of the article I submitted, but in deference to the journal, I would like to ask you to not distribute this article. This is the first review article that will show such a comprehensive review of peer reviewed research on the effects of brainwave entrainment on psychological outcomes. I found 21 studies that met our basic criteria by using a long list of search terms. Many of these terms, such as photic stimulation or auditory stimulation are general terms that can include brainwave entrainment, so I had to search through thousands of studies that were not relevant to my subject of interest. You can see the procedure I used in my methods and figure 1. You will note that I did not use Pubmed, as I was told by the librarian at Tufts University that Ovid searches are more extensive than Pubmed, and include those from Pubmed. A number of the articles are from the Journal of Neurotherapy which can be found in the Psychinfo database.

I acknowledge that there is a huge range in the quality of these studies. While I realize that a controlled study, or even better a double blind controlled study is the gold standard, it is only easy to do with pharmaceuticals. A couple of the popular methods of control include comparing entrainment to music only or just wearing headphones or LED glasses, but the user will almost certainly be able to tell that they are not in the subject group. Another method is to compare 2 separate entrainment frequencies, but each will have their own affects, and thus is less than ideal. On the other hand, I agree that the field should continue to work towards establishing better controls.

In 2006, there was a Brainwave Entrainment Conference at Stanford (See, and there I realized how little most researchers in the field knew about the extent of studies in the field. Thus finding funding and support for their research has been difficult. While the field has been around for over 100 yrs (the first report of brainwave entrainment was in the late 1800’s), it is still has a long way to go. My hope in writing my review article was to adequately describe the current state of the field, so that scientists might gain an interest in the further pursuit of research, and to hopefully increase their prospect for gaining funding to do this important work. Only with adequate funding can we have large scale studies.

Given my research and experience with the field, I do believe that entrainment does have potential to affect a broad range of applications. While most positive findings have been found for various aspects of cognitive functioning, several studies have shown that entrainment can help relieve pain and headaches. There are numerous uses by the industry for other purposes as well, such as relaxation, meditation, sleep and depression. While the peer reviewed research may not yet support those claims (I didn’t look at meditation in my review article), given the infinite number of potential protocols, it may be that studies using better protocols have just not been either scientifically tested, or have not been subjected to peer review. From what I have seen by reports of users and non-peer reviewed research, I am optimistic that brainwave entrainment has the capacity to be effective for a broad range of applications. However, only time and more research will tell.

The studies found in my review article do show long term positive consequences of entrainment with repeated use. We believe that the effects are achieved a lot like learning. Repeated exposure to a stimulus eventually changes the brain to think or work differently. As you know, showing evidence of rewiring of the brain in humans is not possible, but the use of psychological testing before and after do suggest that changes are happening. Studies to determine how long the effects last after cessation of use remain to be done, but the study by Budzynski et al. does show that the positive effects of entrainment extended a school quarter beyond entrainment.

With regards to our website, I have discussed with my boss your concerns about some of the marketing language. Our immediate priority will be changing the website and to take out anything that could be misconstrued. We are also going to highlight the articles that are from peer reviewed sources.

I hope you will read the attached article, and consider updating your blog or adding an addendum to it. We have a very good reputation in the brainwave entrainment community as our intention and primary goal is to provide effective technological solutions to mental health with affordable tools.

Let me know if there are any questions that I can answer for you.


Tina L. Huang, Ph.D.
Director of Research
Transparent Corporation

I appreciate Tina taking the time to read my blog and respond, and she certainly sounds very sincere and straight-forward. However, I disagree with her interpretation of the research, and I think her analysis is very revealing of common errors pervasive on the edges of mainstream medicine.

Reviewing the Literature

Tina is correct in that my searching for articles on brainwave entrainment was not thorough. I did search beyond these terms, and as stated also searched on the names of the authors referenced in the Neuroprogrammer website, but did not do an exhaustive search. That is why I am always careful to say “I did not find any published research” rather than “there is no published research.” As Tina indicated, thorough reviews of the literature are tedious and take many hours of work – which is simply not possible for me to do for a daily blog. I therefore rely upon published reviews – taking advantage of the work of others, which is necessary in any scientific field. I also use more basic searches as an indicator for what is out there. The absence of published studies in listed peer-reviewed journals that deal directly with the claims being made is usually a pretty good indicator.

But now, thanks to Tina, I do have a review article to show me more thoroughly what research has been done. Because the article has not yet been published, and at Tina’s request, I will not reprint the article here. But I did read it and follow up on some of the references, and so will incorporate my impressions into my responses to Tina’s specific points.

Marketing Hype

Tina Wrote: “With regards to our website, I have discussed with my boss your concerns about some of the marketing language. Our immediate priority will be changing the website and to take out anything that could be misconstrued.”

In my previous blog entry I acknowledged that some of the hype on the Neuroprogrammer website was standard marketing fair – but that the standards for medical devices or anything with health claims needs to be higher than those for dishwashing detergent. I am glad she acknowledges there are problems with the website, and I further realize that often within the same company the development team (whether they are scientists, engineers, or programmers) are often not on the same page at the marketing team, who may take it upon themselves to go way beyond the evidence or what the product will do. I have hard developers express such annoyance at their company’s marketers. But this is still no excuse for the company. It is their responsibility to make sure that they are not making health claims for their product that are not supported by adequate evidence. This was, and remains, my primary criticism of this specific company.

Clinical Research

Tina wrote: “While I realize that a controlled study, or even better a double blind controlled study is the gold standard, it is only easy to do with pharmaceuticals.

Too often I have heard this as an excuse for the lack of properly designed clinical trials – whether it’s homeopathy, acupuncture, or therapeutic touch. This is simply not an adequate defense for the lack of reliable clinical evidence. Even if this were true (and I think it isn’t) it does not justify making claims that have not been adequately demonstrated.

Double-blind placebo controlled studies are not limited to pharmaceuticals. This is an absurd double-standard. It may be more difficult, and require some creativity – but well designed studies for non-pharmacological treatments are possible. For example, with brain wave entrainment a control group could be subjected to interventions that require the same amount of time and attention and similar tasks but that are not designed to produce any entrainment. This would be like doing sham acupuncture. Further, whatever mechanism is being used to assess the outcome could be blinded to which treatment group the subjects were in, and the subjects themselves would not have to know if they were getting the treatment or the sham treatment. Many studies also incorporate methods to assess the success of blinding. The simplest way to do this is to give subjects a questionnaire in which they are asked – do you believe you received the treatment or the sham treatment and why, or do you not know?

Tina further wrote: “The studies found in my review article do show long term positive consequences of entrainment with repeated use.

Here is where we simply disagree, the primary reason for which is that Tina is being too generous in her interpretation of the literature. I reviewed the studies she lists in her review article, and they all suffer from serious flaws or limitations.

1 – The primary limitation of all the studies is that the number of subjects were very small, ranging from just a few to 40-50. Small number size makes the results uninterpretable, or preliminary at best.

2 – Inadequate control group and blinding. This is critical for these types of interventions because there is a huge effort and attention component to cognitive performance. There is basically no way to know from these studies if we are seeing a non-specific effect from being studied, or a specific effect from brain wave entrainment.

3 – The studies generally did not adequately control for a learning effect when doing serial assessments. For example, if you give a study subject a test of some cognitive ability, then give them an intervention, then give them the test again there will be a trend toward better performance because there is a learning effect for the test itself. The second or third time the subject does the test they will do better even without any intervention. This should be controlled for by giving subjects the cognitive test several times to establish a baseline, then introducing the intervention and doing follow up testing.

4 – Like any review of published studies, there is no way to completely account for the file-drawer effect. The results of the studies in Tina’s review were generally mixed – some positive and some negative – but she was impressed by the preponderance of positive studies. However, the file-drawer effect (the tendency to publish positive studies and not negative studies) could explain this preponderance. This is partly why reviews and meta-analyses are not a substitute for large, well-designed, definitive clinical trials – which are lacking for any of the therapeutic claims made for brain wave entrainment.


In my opinion, Tina’s optimism is not warranted. The plausibility of therapeutic or performance claims for brain wave entrainment are very low. There is no established mechanism for a specific effect for entrainment, and the explanations given by Tina and the Neuroprogrammer website are vague and unconvincing. They really don’t provide a mechanism at all – just make vague statements about learning or training the brain, or they discuss the mechanisms of entrainment but not how that can relate to any improved performance.

Without a plausible mechanism the threshold for clinical evidence to show that there is actually an effect is high. But so far the clinical evidence does not cross even a low bar for acceptance. Research is preliminary and flawed at best. In my opinion, all of the evidence is perfectly compatible with the null-hypothesis, that there is no specific effect here (I keep saying “specific” effect because there is likely a non-specific effect from doing any mental activity). With low plausibility and weak evidence, the best scientific conclusion we can reach at this time is that brain wave entrainment is probably not useful for any therapeutic purpose.

But – entrainment (unlike homeopathy, for example) is not magic. It is not so implausible that there is no possibility of a specific effect (although I admit I would be surprised if this turns out to be the case), and so I am willing to be convinced if the evidence warrants. What proponents should do – rather than marketing devices with outrageous clinical claims and hyperbole – is do better research. They need to think more about what the mechanism of benefit could be and then investigate those hypotheses. They also need to design and carry out large, well-designed clinical trials. They need to prove that there is a real effect from brain wave entrainment.

If our regulatory laws worked as they should, such evidence would come before these devices are marketed to the public with health claims.

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