Summary: A new analysis highlights how patients’ beliefs about receiving a real versus a placebo neurostimulation treatment can substantially shape outcomes for conditions such as depression and ADHD. Examining five independent datasets, researchers found that participants’ subjective expectations often explained outcome variation as much as—or more than—the treatments themselves.
Across the five studies, the influence of belief varied: in some cases it fully accounted for outcomes, in others it interacted with the actual intervention, and in one study it had no measurable effect. These findings underline the importance of measuring and reporting participants’ beliefs in clinical trials to better interpret treatment efficacy.
Key Facts:
- In four of five neurostimulation studies, participants’ beliefs about whether they received an active or sham treatment significantly affected outcomes.
- Belief-related effects sometimes outweighed the measurable effect of the actual treatment.
- The authors recommend routinely recording subjective treatment beliefs to improve interpretation of clinical and cognitive intervention studies.
Source: University of Surrey
Considering whether people believe they are receiving a genuine treatment or a placebo can offer clearer insights and help improve interventions for conditions such as depression and ADHD.
A team of psychologists led by Professor Roi Cohen Kadosh at the University of Surrey reanalyzed five independent neurostimulation studies to assess the role of participants’ subjective beliefs. The pooled datasets included clinical patients treated for depression and ADHD as well as healthy adult volunteers across a range of ages and stimulation methods.
Overall, subjective beliefs about receiving active versus sham stimulation accounted for outcome variability in four of the five studies. In several cases, participants’ expectations provided a better explanation for improvements than the objective treatment assignment. Beliefs about the intensity of the intervention also influenced outcomes in certain studies.
Professor Roi Cohen Kadosh explains the implication for clinical research:
“It is often assumed that identical medical procedures will produce comparable outcomes across patients. Our analysis reveals a different picture: the same neurostimulation protocol can yield widely varying results depending on what participants believe about the treatment. In some instances, belief alone—when a person thinks they received an effective treatment—was associated with marked improvement, even if the intervention was a placebo.”
Study details:
– Study 1: Among 121 participants receiving various forms of repetitive Transcranial Magnetic Stimulation (rTMS) for depression, perceptions of whether treatment was real or sham were more closely linked to reduced depression symptoms than the rTMS type itself.
– Study 2: In 52 older adults with late-life depression undergoing deep rTMS (active or sham), outcomes depended on the interaction between actual treatment and participants’ beliefs about receiving real or placebo stimulation.
– Study 3: A home-based transcranial Direct Current Stimulation (tDCS) trial with 64 adults diagnosed with ADHD found that both the actual stimulation and participants’ beliefs independently contributed to reductions in inattention scores.
– Study 4: Among 150 healthy volunteers given varying tDCS doses to probe mind-wandering, those who believed they had received a stronger dose reported greater mind-wandering, regardless of the objective dose.
– Study 5: In an investigation of transcranial random noise stimulation and working memory, participants’ beliefs did not affect outcomes, demonstrating that belief effects are not uniform across all neurostimulation paradigms.
Together, these datasets illustrate a spectrum of effects: subjective beliefs can fully explain treatment responses, can interact with the active intervention, or may have no measurable influence depending on the context and outcome measured.
Dr Shachar Hochman, co-author and researcher at the University of Surrey, notes:
“Placebo and sham effects are a recognized phenomenon, but they have often been treated separately from analyses of objective treatment effects. By combining subjective belief measures with objective outcomes, we can better understand where treatment effects originate and how expectations shape results.”
Professor Cohen Kadosh adds:
“Recording participants’ beliefs at multiple time points during trials could add important explanatory power to clinical studies. This practice may be valuable not only for neurostimulation but also for pharmacological trials and emerging interventions such as virtual reality. We encourage researchers to use this combined-approach to reassess past findings and to incorporate belief measures in future work.”
About this psychology research news
Author: Dalitso Njolinjo
Source: University of Surrey
Contact: Dalitso Njolinjo – University of Surrey
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The Importance of Individual Beliefs in Assessing Treatment Efficacy: Insights from Neurostimulation Studies” by Roi Cohen Kadosh et al. eLife
Abstract
The Importance of Individual Beliefs in Assessing Treatment Efficacy: Insights from Neurostimulation Studies
Debates about the effectiveness of interventions—ranging from neurostimulation and neurofeedback to cognitive training and pharmacotherapy—often reflect mixed experimental results. Standard practice compares outcomes between active and placebo conditions, but this approach can overlook participants’ subjective experiences of which treatment they believe they received.
In this work, we show that individual differences in subjective treatment belief (the perception of having received the active versus placebo condition) can explain outcome variability more effectively than objective treatment assignment. We analyzed four independent datasets totaling 387 participants, including clinical patients and healthy adults across different age groups, exposed to transcranial magnetic stimulation (Studies 1 & 2) and transcranial direct current stimulation (Studies 3 & 4).
Across datasets, models that included subjective treatment provided better fits than models relying on objective treatment alone. These results highlight the substantial contribution of subjective experience to clinical, cognitive, and behavioral outcomes and support the routine inclusion of belief measures in both existing and future studies to improve estimation of true treatment effects and enhance reproducibility of interventions.