According to the Medical Expenditure Panel Survey, about 100 million adult Americans live in pain. Prescription medications are very successful in blunting the perception of pain, however adverse effects are broad. To name a few, they include constipation, nausea, lethargy and not uncommonly, death. In 2014, 2 million Americans abused or were dependent on opioids and 160,000 have died since 1999. The need for alternative treatments for pain is evident. Early research into the utilization of virtual reality (VR) for both acute and chronic pain is promising.
The theory behind VR’s mechanism of action is firmly embedded within principles of psychology. By diverting attention away from a pain sensation towards a competing stimulus, such as a video screen that engages the body and senses through an immersive experience, the brain can refocus attention towards an enjoyable experience, and consequently the pain pathways are attenuated. A study published by Johnson and Coxon demonstrated the impact targeting two versus one sense had on pain tolerance. The study looked at 27 healthy volunteers and submerged their non-dominant hand in freezing water (around 1⁰ C or 33⁰ F). They had participants wear a head mounted display (HMD) and noise-canceling headphones. The study used a within-participant design, and obtained baseline pain data by applying freezing water without the HMD or music. They then exposed each participants to each variable: an immersive driving game with music, the immersive driving game without music, and no immersive game with music. The results demonstrated that the immersive content without sound and sound alone were able to significantly decrease pain as compared to the baseline. Furthermore, the combination of immersive content and sound had the greatest significant impact on pain tolerance. These interesting findings allude to the power of combining the senses in unique ways to refocus the brain for overcoming a painful experience.
A study by one of the leading experts in the field, Dr. Hunter Hoffman, compared an active VR experience (SnowWorld) versus no VR experience, demonstrated a statistically significant decrease in overall worst pain, time spent thinking about pain, and unpleasantness of the pain in the active VR experience group. Furthermore, the study included fMRI data for each participant and showed a decrease in pain-related brain activity in the anterior cingulate cortex, primary and secondary somatosensory cortex, insula and thalamus. The fMRI studies also showed an increase in activation of the prefrontal cortex. These findings are consistent with those of prior studies that utilized the counting Stroop test to show significantly diminished pain intensity scores by subjects performing a mentally taxing task resulting from cognitive-interference. A counting Stroop differs from the traditional Stroop test in that it asks participants how many words appear on the screen regardless of the meaning of the words. In a traditional Stroop example, the participants are shown a word that specifies a color; however, the actual color of the text may differ from what the word specifies, but the correct answer is the color the word specifies.
Examples of single trials for the two types of stimuli. Both sets of word stimuli are common words from a single semantic category. During ‘neutral’ trials, common animal names (dog, cat, bird, or mouse) are used. During ‘interference’ blocks, the words consist of number names (one, two, three, or four). In both examples, the correct answer would be to press button number 4. Bush et al 2006, used under license by NPG.
In a study published in Cyberpsychology, Behavior, and Social Networking, investigators created three groups and immersed all participants’ non-dominant hands in freezing water temperatures. One group had a Virtual Reality experience that displayed objects that defied the law of physics, another displayed sharp objects with irritating sounds that were intended to symbolize pain, and the last group had no VR experience. Participants in the sharp object and irritating sound group were instructed to manipulate the objects so the edges became rounded and the sounds became more peaceful. The results showed that those that had control over the objects reported having an increased sense of self-efficacy for tolerating pain and for reducing pain intensity. Without overstating the benefit, this study suggests that VR interventions can have a positive impact on cognition and augment pain-coping skills, which ultimately may lead to an increased ability to tolerate a lower amount of pain medications or remove the need completely.
The pain reducing ability of VR has also been observed in chronic pain patients as well. In a study by Jones, Moore & Choo (currently in review for publication) it was found that among chronic pain patients who played the VR game Cool!, 94% of patients had at least some pain relief during the VR experience and 92% had at least some relief after the experience had completely finished. This finding suggests that VR’s effects may last beyond the period of application in a similar fashion to a medication; however, the “half-life” is still unknown.
VR has shown to be therapeutic for burn patients too. One study assessed VR’s application during wound debridement and found a statistically significant decrease in visual analog scale pain scores over the first three sessions of wound debridement. By decreasing the pain of this procedure, patients’ outlook can be positively impacted which can have implications for mood, motivation, and overall satisfaction. Studies such as these that explore the various use cases for VR are paramount. While VR’s application in healthcare is very exciting, there is a strong need for further research to substantiate these early findings and validate the efficacy, dosing, content, adverse effects, and additional use cases.
Brian Mayrsohn is a fourth year medical student pursuing a career in Physical Medicine and Rehabilitation. He is interested in the applications of emerging and existing technologies to the medical field.
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