In clinical trials, scientists give one group of patients the active intervention that is being studied and give another group an inactive placebo—a fake version of the real intervention. In the best designed studies, both the researchers and the participants are blinded, meaning no one knows who is receiving which treatment until the end of the study.

A significant percentage of patients receiving a placebo report an improvement in their symptoms. No one knows why the placebo effect occurs, but one theory points to a patient’s expectations of treatment—if he or she believes the treatment will be helpful, improvements are more likely to be reported, whether the treatment is active or a placebo.

The placebo effect occurs more often in conditions that are chronic and lacking a clear physical cause. Therefore, it should be common among patients with chronic fatigue syndrome (CFS), at least in theory. CFS is characterized by severe physical and mental fatigue that lasts at least six consecutive months, and cannot be explained by any known medical condition. Other symptoms of CFS include muscle pain, joint pain, sleep disturbance, impaired memory, mood disturbance, and headache. CFS is without a known cause or cure. Some researchers believe, however, that emotional or social stresses combined with other triggers (e.g., viral infection or minor trauma) contribute to the disorder. Additional factors, including a sedentary lifestyle, may encourage the symptoms to become chronic. Many patients, though, are firm believers that CFS is strictly a medical condition, and are resistant to psychological explanations or interventions. Irrespective of its cause, patients and their doctors agree that CFS is a complex condition that is very difficult to treat. It leaves many patients frustrated and can strain the doctor-patient relationship.

It has generally been accepted that CFS patients are more likely to experience the placebo effect during treatment than patients suffering from conditions with identifiable causes. In 1997, the Royal Australasian College of Physicians stated that 30% to 50% of people with CFS will report improvement while on placebo. However, there has been no systematic approach taken to confirm this widely held belief. Therefore, a group of researchers from King’s College in London pooled all the existing data on the topic to quantify the placebo effect among patients with CFS. As they report in the March-April 2005 issue of Psychosomatic Medicine , the overall placebo effect was actually lower in people with CFS than with other medical conditions.

About the Study

The researchers scoured the medical literature published between January 2000 and December 2002 to find clinical trials enrolling people with CFS. Studies that met specific criteria were selected for this meta-analysis. Being a clinical trial, whether randomized or not, was the first criterion. Another stipulation was that a patient’s response to placebo was indicated as either “improved or not” or “responded or not.”

In a meta-analysis, researchers combine and analyze the findings of several studies on the same topic. From this volume of data, the researchers can often tease out information that the individual studies were unable to uncover.

The Findings

Twenty-nine studies, representing 1,016 CFS patients, met the criteria for inclusion in this meta-analysis. The reported placebo responses ranged from 5.9% to 50%, with an average of 19.6%. In other words, roughly one-fifth of patients on average reported that their symptoms improved while taking a placebo, a low proportion compared to placebo-controlled studies involving other conditions.

As expected, the placebo response was lowest (14%) in studies of psychological interventions for CFS, and highest (24%) in trials of non-psychological interventions. Since people dealing with CFS tend to attribute their disease to a physical, rather than mental, origin, they may have lower expectations for improvement in studies focused on psychologically-based interventions.

How Does This Affect You?

While this study did not confirm that the placebo effect is more common among patients with CFS than those with other chronic conditions, it did confirm that CFS is a complicated and mysterious disease. The study’s authors attempt to explain their observations by suggesting that CFS patients have grown so skeptical that their expectations for improvement with any treatment are low.

If you are living with CFS, it is essential to find a doctor you can trust and who appreciates the complexity of this condition. While an expectation of improvement is essential for recovery, relying on the placebo effect alone is no substitute for a serious plan of action. The best treatment approach at this time appears to be a multi-faceted one. Medications can be given to treat specific symptoms, while a combination of graded exercise therapy (GET) and cognitive-behavioral therapy (CBT) have shown promise for some patients. In addition, your doctor or a rehabilitation medicine specialist can guide you in establishing daily routines that can help you to adapt to the strain of CFS.