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)
