Miscellaneous neurologic conditions with a few or no available data.

In this chapter, we will review the available literature on the nature of the placebo effect in conditions that are not well studied in terms of their response to the placebo intervention such as fatigue in general and in the context of myasthenia gravis and chronic fatigue syndrome, insomnia, restless leg syndrome, and central conditions such as multiple sclerosis. The clinical trials are either small or lack a natural history arm or a real placebo arm, therefore no definitive conclusions can be drawn regarding the magnitude and possible mechanisms of the placebo effect in these conditions. In addition, we will review some studies in conditions other than neurology, such as cardiovascular, respiratory, gastrointestinal, and genitourinary diseases that can be of some interest to neurologists. Overall, we know very little, if any, about the psychobiological underpinnings in these medical conditions, and this lack of knowledge must be the stimulus for the pursuit of new future research.