Placebos are faux medications - typically lactose or microcrystalline cellulose - designed to act as inert, non-functional 'controls' in medical experiments. (There are also faux medical procedures, see section below)

From the beginnings of their use in research, experimenters had assumed that they could not possibly have any medical effect. But they are now being taken seriously as treatments, after it was discovered that totally inactive substances can have profoundly beneficial effects in a wide range of medical conditions.

After four decades of probing the mechanisms of placebo responses, researchers are advancing the argument that inert pills are more than just negative controls in clinical trials: they can be a treatment in their own right."

Source Nature Vol 535, July 2016

The mechanism(s) by which they operate - which can only be psychological - are not yet explained. The implication being that many individuals, in many circumstances, somehow have the power to improve their adverse medical conditions at will (though this facility is normally suppressed).

Several recent experiments have examined the effects so-called Open Label placebos - that's to say medical trials in which the recipients are informed that they will be taking a completely inert substance. Even so, despite patients knowing that they're receiving a placebo, several such trials have revealed that the placebos can still have substantial beneficial effects. See example here. Trials 18, 234.

(Note that Open Label trials also exempt researchers from any ethical problems in giving inert medications to patients who are unwell.)

A 2022 study from the University Medical Center Hamburg-Eppendorf,Hamburg, Germany, found that placebos with deliberately built-in unpleasant side-effects can work better than plain placebos. See: How side effects can improve treatment efficacy: a randomized trial

Extensive further resources : Program in Placebo Studies & Therapeutic Encounter (PiPS) at Harvard University, US.

As the relevance of the placebo effect becomes more obvious, it's now assumed that many medical 'treatments' - ones to which the medical establishment can't assign any scientific basis - can nevertheless still be effective. It also throws into focus the idea that some medications which relieve symptoms might sometimes be acting via their 'placebo' routes rather than through chemical effects (for a well-known example, see paracetamolplugin-autotooltip__plain plugin-autotooltip_bigParacetamol

"Acetaminophen (INN Paracetamol) is one of the most widely used over-the-counter antipyretic and analgesic drugs worldwide. [...] Although discovered more than 100 years ago, and used extensively for ~ 50 years, its mode of action is still unclear)

The placebo effect is not restricted to drug treatments: increasing attention is being given to its effect in surgical procedures. A 2014 paper published in the British Medical Journal found that :

Placebo controlled trial is a powerful, feasible way of showing the efficacy of surgical procedures. The risks of adverse effects associated with the placebo are small. In half of the studies, the results provide evidence against continued use of the investigated surgical procedures. Without well designed placebo controlled trials of surgery, ineffective treatment may continue unchallenged."

The study found that many (minor) routine surgical procedures often have little or no real medical effects, but are nonetheless effective because of their 'perceived' benefits.

See:Use of placebo controls in the evaluation of surgery: systematic review

A similar scenario has emerged regarding recent studies looking into the efficacy of arterial stents. A 2018 article in the New York Times points to a growing number of studies which have shown that (in most cases) arterial stents to combat angina have little or no medical value - but they do help angina sufferers because of a pronounced placebo effect.

See: Heart Stents Are Useless for Most Stable Patients. They’re Still Widely Used.

Note: An associated effect, called the 'Nocebo' effect, is when a patient reacts badly to a placebo (i.e. by becoming ill or being made worse). As above, there is as yet no explanation as to how this might happen.

Importance Rating