Virtual reality and non-invasive brain stimulation for rehabilitation applications: a systematic review.

Thirteen of the sixteen studies did not test VR and brain stimulation separately, so it is impossible to know whether any benefit came from the combination, from VR alone, or from stimulation alone. Sample sizes were very small, ranging from 1 to 108 participants per study, with an average of 38. The authors themselves identified small sample size as the most frequent limitation across the reviewed papers. Blinding was inconsistent: only six of sixteen studies were double-blind. In one spider phobia study, participants reported sensations during active stimulation that may have unblinded them. The review excluded study protocols and non-interactive VR, but did not assess risk of bias or conduct a meta-analysis, so the overall quality of the included evidence was not formally graded. Many stroke patients in the subacute phase were included, a period when spontaneous recovery occurs, making it difficult to attribute improvement to the intervention. The review authors note that VR protocol details such as specific game mini-levels and timing pauses between techniques were often missing, limiting reproducibility.

The paper is categorised as research supported by non-U.S. government sources. No specific funding body, commercial sponsor, or author disclosure is named in the supplied text.

Do not read the nine positive studies as evidence that adding brain stimulation to VR is better than VR alone. Only three studies tested the components separately, and in the others it is impossible to tell whether the benefit came from VR, from stimulation, or from their combination. A therapist who assumes the combination is necessary may add a costly and time-consuming intervention with no proven advantage over the VR component they are already delivering.