Previous Experiences with Treatments Influence Effectiveness of New Treatments


Previous experiences of treatments working or not working significantly influence the effectiveness of new treatments on clinical trial participants and patients, even in relation to entirely new treatment approaches, according to a study in PLOS One. This ‘psychological bias’ was even detectable through brain imaging of people’s responses to painkillers, the German research team found. They argued that this has significant ramifications, particularly for the treatment of chronic physical or psychological conditions.

In the study, forty blinded participants were given either a placebo or an actual analgesic (painkiller) alternately via a patch and an ointment, and in different orders. They were asked to indicate the effectiveness of the treatment in each case, while their brain responses were monitored and a heat source was administered on their forearms near their pain threshold.

Participants who’d had a negative first experience with the “effectiveness” of the analgesic, because they’d actually had a placebo in the first phase of the trial, subsequently found the actual analgesic less effective in the second phase. Conversely, participants who’d had a positive experience of the analgesic working well in the first phase, subsequently felt like the placebos were working relatively effectively in the second phase. These legacy effects from previous experiences continued even when the mode of treatment was changed. Patients who were feeling particularly anxious or depressed were the most susceptible.

“These results significantly extend previous findings by showing that the influence of treatment history transfers over time and over therapeutic approach,” wrote the researchers.

“(O)ur study provides evidence that treatment history critically determines the response to a subsequent treatment at a behavioral and neurobiological level,” the researchers wrote. “Further, we show that the susceptibility for carry-over effects varies across individuals and is associated with trait anxiety and depression. Given the large number of patients with persisting health problems despite various treatment attempts, it seems reasonable to assume that negative treatment experiences and their detrimental effects for subsequent treatment approaches contribute substantially to increased health care costs and importantly, to prolonged suffering of our patients. Even though these experimental findings require replication in larger clinical populations, we feel that awareness of this effect is mandatory for every physician and concerted effort is required to avoid or overcome the negative effects of prior experience on treatment outcome.”

(Full text) The Effect of Treatment History on Therapeutic Outcome: Psychological and Neurobiological Underpinnings (Kessner, Simon et al. PLOS One. October 2, 2014. DOI: 10.1371/journal.pone.0109014)


  1. So what is the effect on later attempts at “treatment” if your first experience is being hauled off by police to the ER, put in restraints, held against your will in a hospital ward with other people there against their wills, some of whom seem kind of scary, and forcibly injected with drugs that massively alter your perception of reality, often in a negative way? Think that maybe such treatment might lead to a psychological “bias” that these people’s “treatments” aren’t anything you want to try again?

    —- Steve

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    • I can tell you: you never take any of that s**t ever again even if someone pays you a million dollars and are prepared to kill if one would threaten in forcing you to take it. Plus you make sure nobody you know and care for ever gets close to the whole bunch.
      For these people reasons for why things work the way they work and why things happen are irrelevant. They are just trying to get around reality to obtain results they want. That’s why they are starting to “research” placebo effect in ways which make me think they will use it to manipulate trials even further. Call me paranoid but I have negative trust in the whole business.

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    • I must say I think all mainstream doctors are starting to look like complete fools for advocating belief in psychiatry. At least I know I didn’t lose respect or hope in medical cures from just psychiatry, after dealing with those psychos, I lost faith in and respect for all of mainstream medicine.

      Is it really wise to advocate belief in a fraudulent field of medicine (no doubt, for unethical reasons), if the respectability of the entire medical field ends up suffering due to such lies? I don’t think so.

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  2. It’s pretty easy to see how this knowledge is likely to affect drug trials – the drug companies will seek to only allow into the trials people who have had positive responses to previous treatments! They may have to find clever ways of doing this so that it isn’t obvious that this is what they are doing though…..

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    • They can do that out in the open and claim that they are “removing the bias”. It’s not the only of recent research on placebo effect that has quite ominously sounding commentary of “potentially improving clinical trial design”.

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  3. I’ve only looked at the article briefly, but I’m confused as to how an experiment in which people are burned on their arms is translatable to people receiving care (or poor “care”) in a healthcare setting? I get the whole initial positive / negative experience affects future experiences, that’s common sense. I just don’t see how such a particular experiment can claim to come to a conclusion about a healthcare environment.

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