Placebo Effect

Effects

-Large effect seen with analgesia: effect in many cases seems to be based on expectation (if they think it's gonna benefit them, it's gonna benefit them) -psychiatric medicine: placebo is comparable to antidepressants in effectivenss (only severe cases of depression saw more benefit from antidepressants; even cases that were given th drug likely experienced a placebo effect) -Kaptchuk: patients were given either no treatmnet of open-label placebo for IBS; open-label placebo was linked to improvement in symptoms; people knew they were taking the placebo; people getting placebo did better than no treatment people

Henry Beecher

-after seeing placebo effect in injured soldiers, Beecher advocated incororation into drug testing (individuals being told they were being given morphine seemed to feel less pain)

Early History

-at the turn of 18th century, use of inert treatments was still fairly common -Haygarth & Perkins tractors in 1801 may have been the first placebo-controlled trial: Perkins told people he could cute them by hovering two metal rods over their body. Haygarth, a doctor, did the same thing but with metal rods and wooden rods and BOTH groups said they felt better. So there was nothing special about the metal rods, people were just experiencing the placebo effect -studies in 1930s found placebo to be as effective as vaccines to prevent colds -first time word "placebo" was used in reference to control treatment in trial

Requirement of beating placebo in 2 trials

-in 1962, congress required clinical trials for drug approval to be well-controlled, which usually involved a placebo -medicines must beat placebo in 2 trials today to be approved by the FDA

Nocebo

-inert substane that causes adverse effects -percieved possibility of side effects increases liklihood they occur -finasteride and erectile dysfunction: one group was told that erective dysfunction was a side effect and that group reported drastically higher rates of erectile dysfunction, just because they thought it was going to happen -when informed of side effects, they are more likely to occur

Physiological basis

-naloxone can be used to block pain-relieving effects of placebo; this finding led to the discovery that placebos can influence levels of endogenous opioids (these can effect pain, heart rate, respiration...) -placebo effects in parkinson's disease tratmnet have been associated with increases in dopamine levels in the brain -studies of appetite have found that ghrelin levels can be reduced by telling someone they have eaten more calories

Hrobartsson and Gotzsche

-review found certain things could influence probability of observing placebo effect -found placebo effect only in patient reported outcomes (not observer reported outcomes) and only when patients used a continuous scale -reporting bias -people may report feeling better because they think that's what someone wants to hear