Editing Placebo (section)

===Factors influencing the power of the placebo effect===
A review published in ''[[JAMA Psychiatry]]'' found that, in trials of antipsychotic medications, the change in response to receiving a placebo had increased significantly between 1960 and 2013. The review's authors identified several factors that could be responsible for this change, including inflation of baseline scores and enrollment of fewer severely ill patients.<ref>{{cite journal | vauthors = Rutherford BR, Pott E, Tandler JM, [[Melanie Wall|Wall MM]], Roose SP, Lieberman JA | title = Placebo response in antipsychotic clinical trials: a meta-analysis | journal = JAMA Psychiatry | volume = 71 | issue = 12 | pages = 1409–21 | date = December 2014 | pmid = 25321611 | pmc = 4256120 | doi = 10.1001/jamapsychiatry.2014.1319 }}</ref> Another analysis published in ''Pain'' in 2015 found that placebo responses had increased considerably in [[neuropathic pain]] clinical trials conducted in the United States from 1990 to 2013. The researchers suggested that this may be because such trials have "increased in study size and length" during this time period.<ref>{{cite journal | vauthors = Tuttle AH, Tohyama S, Ramsay T, Kimmelman J, Schweinhardt P, Bennett GJ, Mogil JS | title = Increasing placebo responses over time in U.S. clinical trials of neuropathic pain | journal = Pain | volume = 156 | issue = 12 | pages = 2616–26 | date = December 2015 | pmid = 26307858 | doi = 10.1097/j.pain.0000000000000333 | s2cid = 23246031 }}
* {{lay source |template = cite magazine|vauthors = Dahl M |url= https://www.thecut.com/2015/10/placebo-effect-is-getting-stronger.html|title = The Placebo Effect Is Getting Stronger — But Only in the U.S.|date = October 9, 2015 |website = The Cut}}</ref>

Individual differences in personality traits may influence susceptibility to placebo and nocebo (negative placebo) effects. People with a more optimistic outlook tend to exhibit stronger placebo responses, while those with higher levels of anxiety are more likely to experience nocebo effects.<ref>{{cite journal | last=Kern | first=Alexandra | last2=Kramm | first2=Christoph | last3=Witt | first3=Claudia M. | last4=Barth | first4=Jürgen | title=The influence of personality traits on the placebo/nocebo response | journal=Journal of Psychosomatic Research | publisher=Elsevier BV | volume=128 | year=2020 | issn=0022-3999 | doi=10.1016/j.jpsychores.2019.109866 | doi-access=free | page=109866 | url=https://www.zora.uzh.ch/id/eprint/183343/9/Kern_et_al._%282020%29_Manuskript.pdf | access-date=2025-04-09}}</ref>

[[childhood|Children]] seem to have a greater response than [[adults]] to placebos.<ref>{{cite journal | vauthors = Rheims S, Cucherat M, Arzimanoglou A, Ryvlin P | title = Greater response to placebo in children than in adults: a systematic review and meta-analysis in drug-resistant partial epilepsy | journal = PLOS Medicine | volume = 5 | issue = 8 | pages = e166 | date = August 2008 | pmid = 18700812 | pmc = 2504483 | doi = 10.1371/journal.pmed.0050166 | editor1-last = Klassen | editor1-first = Terry | doi-access = free }}</ref>

The administration of the placebos can determine the placebo effect strength. Studies have found that taking more pills would strengthen the effect. Capsules appear to be more influential than pills, and injections are even stronger than capsules.<ref name="Rosenberg2010_176">{{cite book |last1=Rosenberg |first1=Robin |last2=Kosslyn |first2=Stephen |title=Abnormal Psychology |date=2010 |publisher=Worth Publishers |isbn=978-1-4292-6356-6 |page=176 |url=https://books.google.com/books?id=2Nh-RAAACAAJ |access-date=7 December 2020 |language=en}}</ref>

Some studies have investigated the use of placebos where the patient is fully aware that the treatment is inert, known as an ''[[Open-label trial|open-label placebo]]''. Clinical trials found that open-label placebos may have positive effects in comparison to no treatment, which may open new avenues for treatments,<ref name="Blease2019">{{cite journal |last1=Blease |first1=CR |last2=Bernstein |first2=MH |last3=Locher |first3=C |date=26 June 2019 |title=Open-label placebo clinical trials: is it the rationale, the interaction or the pill? |journal=BMJ Evidence-Based Medicine |type=Review |volume=25 |issue=5 |pages=bmjebm–2019–111209 |doi=10.1136/bmjebm-2019-111209 |pmc=6930978 |pmid=31243047}}</ref> but a review of such trials noted that they were done with a small number of participants and hence should be interpreted with "caution" until further, better-controlled trials are conducted.<ref name="onlinelibrary.wiley.com">{{cite journal |title=Effects of placebos without deception compared with no treatment: A systematic review and meta-analysis |date=2017 |doi=10.1111/jebm.12251 |last1=Charlesworth |first1=James E.G. |last2=Petkovic |first2=Grace |last3=Kelley |first3=John M. |last4=Hunter |first4=Monika |last5=Onakpoya |first5=Igho |last6=Roberts |first6=Nia |last7=Miller |first7=Franklin G. |last8=Howick |first8=Jeremy |journal=Journal of Evidence-Based Medicine |volume=10 |issue=2 |pages=97–107 |pmid=28452193 |s2cid=4577402 |doi-access=free }}</ref> An updated 2021 systematic review and meta-analysis based on 11 studies also found a significant, albeit slightly smaller overall effect of open-label placebos, while noting that "research on OLPs is still in its infancy".<ref>{{Cite journal |last1=von Wernsdorff |first1=Melina |last2=Loef |first2=Martin |last3=Tuschen-Caffier |first3=Brunna |last4=Schmidt |first4=Stefan |date=2023 |title=Effects of open-label placebos in clinical trials: a systematic review and meta-analysis |journal=Scientific Reports |language= |volume=11 |issue=1 |pages=3855 |bibcode=2021NatSR..11.3855V |doi=10.1038/s41598-021-83148-6 |issn= |pmc=7887232 |pmid=33594150}}</ref>

If the person dispensing the placebo shows their care towards the patient, is friendly and sympathetic, or has a high expectation of a treatment's success, then the placebo is more effectual.<ref name="Rosenberg2010_176" />