Eighteen studies were analyzed, in which a total of 853 patients were treated with cranial electrotherapy stimulation (CES) for depression. The patients had presented with various clinical syndromes, of which depression played a major part. The treatment outcome depression scores were combined statistically in order to get a more confident look at the effectiveness of CES for treating this condition. While many of the studies were of the classic double blind protocol, others used either the single blind, the cross over design or were open clinical trials. The result of the analysis showed that the overall effectiveness of CES was 47% improvement. The results indicated that various types of depression, which accompany a wide range of clinical syndromes can be expected to respond, sometimes dramatically to CES treatment.

The goal of clinical studies is always to first test the effectiveness of a potential treatment and secondly to discover which patients the treatment may be most effective in treating. Meta-analysis has the effect of allowing researchers to essentially study a larger number of patients than can usually be assembled for a single study, and the larger the combined study sample, the greater is the confidence that can be placed in the study outcome: that the study findings are true and accurate. Also, the more diverse the study group is in the combined sample, the more confident one can be in generalizing the study outcome to larger groups of patients outside the study. That is, it increases the range of potential types of depression patients that we can predict will be effectively treated with CES.

In the table below is a summary of 18 studies that were combined into the meta-analysis reported on here.

a Correlation scores, representing percent improvement, are obtained mathematically from the study outcomes presented by the authors. Scores such as percent change scores, the statistical probability scores reported, F scores, t scores, and the like, are changed to r correlation scores and then into Zr scores. That is because percent improvement scores can not legally be averaged. The Zr scores are then averaged and converted back to percent improvement (effect size.)

b Most of the rating scales, both by the patients and the clinicians were of published reliability and validity. In many of the studies, more than one measure of depression was used. In those cases, the average of the results was calculated and reported as the overall result of the study.

c Effect size, here, is a statistician’s basic estimate of the overall percentage improvement by the patients as a result of the treatment

In many of the studies, depression was but one symptom within a larger presenting syndrome. For example in many of the patients, fibromyalgia was the presenting symptom, while in another large group of studies substance abuse (drug abstinence syndrome) was the presenting diagnosis. The presenting syndrome or type of patient is given in column three of the table. In all of the studies, however, depression was a major diagnosis within the presenting syndrome or group.

In the open clinical study, the patients know they are being actively treated for their depression, the clinicians know who is being treated, and the statistician who summarizes the study data also knows, since there is only one group of patients.