Sometimes patients claim a beneficial or adverse effect to a therapy which appears to contain no active ingredient. These can be misleading if not recognized or understood.
placebo effect = beneficial effect ascribed to a medication with no active ingredient. I would include homeopathic remedies in this class.
nocebo effect = nonspecific side effect ascribed to a medication
Possible causes for an unexplained benefit or adverse event to a medication:
(1) other medications or herbal supplements that the patient may be taking
(2) relapsing underlying disease (either improving or worsening)
(3) psychological belief of benefit or harm
(4) something present in the formulation that was not specified or else was thought to be innocuous
(5) nonspecific somatic complaint
(6) onset of another disorder (for adverse effect)
where:
• An unspecified additive might be another drug or might be a component to which the patient has an allergy.
• A somatic complaint that improves may be felt to be a positive effect, while one with a new onset may be viewed as an adverse effect.
• A person's belief in benefit or for harm can be based on things that the physician says, on what others have claimed, on cultural or religious beliefs, or from things that the patient has read.
It is important not to assume that an apparent placebo or nocebo effect merely reflects a psychological state, although this should be recognized as a possibility if the other explanations have been excluded.