Blog 3: Electrical stimulation and the placebo effect on chronic pain

Although much of the literature reports that electrical stimulation treatment for chronic pain is not as successful as treatment for acute pain, we feel that there are some significant findings worth mentioning.

Cohen (1994) reported that almost 25% of 1000 chronic pain patients treated with TENS had their pain relieved to the point at which no other therapy was necessary.  Long and Hagfors (1995) found that 25-30% of 3000 patients surveyed across five different pain centres, who were previously incapacitated by pain, had significant pain relief with TENS alone. Robinson (1996) reviewed a number of studies in the use of TENS to control both acute and chronic pain related to musculoskeletal disorders.  From the review, it was concluded that although TENS is capable of producing clinically relevant pain relief, the pain relief is often of short duration and therefore only a small percentage of patients achieve lasting pain relief. 

In comparison, Beecher (1992) determined that an average of 35% of patients obtained satisfactory pain relief from placebo treatment, although some studies have reported 100% of patients respond positively to placebos (Wall, 1994).  The study by Wall was found to be a stand-alone case therefore we find the complete positive effect difficult to agree with, especially with the decent amount of conflicting literature. In support of this, Langley and colleagues (1994) noted that placebo studies may be inappropriate as the patient can distinguish active from inactive TENS – therefore making it highly unlikely that a placebo positive response rate could reach 100% as suggested by Wall.

However, we did come across a study in which the investigators used methods of ‘strong suggestion’ whilst administering placebo treatments to patients. This encouraged patient mentality to be influenced towards truly believing they were receiving TENS. In doing so, Deyo and colleagues may have in fact enhanced the placebo impact on pain which was found to be similar to the effects achieved from active TENS.  

Figure 3.0 Portable TENS machine readily available to the public

 http://static.medshop.com.au/images/D/17841_MES_Everyway_EV906_4_Channel_Digital_Tens_EMS_Machines.jpg 

In relation to our previous post, although a specific analgesic effect for TENS has not been conclusively proven in the treatment of chronic pain, the brief results mentioned speak for themselves.  The assessment of long-term pain relief with TENS on chronic pain is difficult as the studies are complicated to conduct and researchers use different criteria and guidelines to judge successful pain relief.  After considering the positive outcomes shown through the use of TENS along with the evidence for placebo effects, we are left wondering if there can be a combination of the two. Does receiving treatment with TENS cause clinical pain relief that is enhanced by a belief that it will work (therefore, the placebo effect)?  In our opinion, regardless of whether the mechanism of pain relief for chronic pain sufferers is analgesic- or placebo-based, these patients are still being offered a treatment modality which may provide much needed pain relief.  Successful patient management should incorporate a trial of TENS as part of an overall care plan that includes the control of pain.