Placebos could help to treat depression and ADHD

Taking into account whether people believe they are receiving a real treatment or a placebo could help improve interventions for conditions such as depression and ADHD, according to a team of psychologists led by Professor Roi Cohen Kadosh from the University of Surrey.

Having analysed five independent studies that covered different types of neurostimulation treatments, the researchers found that patients’ beliefs about whether they were receiving real or placebo treatments explained the treatment outcomes in four of the five studies — on some occasions, better than the actual treatment itself. Their results were published in the journal eLife.

“The concept that a placebo … can mimic genuine treatment effects is well established in science,” said Surrey’s Dr Shachar Hochman. “While researchers have closely monitored this phenomenon, it has been typically catalogued separately from the in-depth analyses of the actual treatment outcomes. What sets our study apart is that we have brought together these two datasets — subjective beliefs and objective treatment measures. This has the potential to reveal new insights into treatment efficacy.”

In the first study, 121 participants were treated with different forms of transcranial magnetic stimulation (rTMS) for depression. The results showed that participants’ perceptions about receiving real or placebo treatment mattered more than the actual type of rTMS in reducing depression.

The second study involved 52 older people with late-life depression who received either a real or placebo of deep rTMS. The effect of treatment on reducing depression scores depended on the combination of the participants’ perceptions about receiving real or placebo treatment and the actual treatment they received.

In the third dataset, researchers investigated the effects of home-based transcranial direct current stimulation (tDCS) treatment on 64 adults diagnosed with ADHD. At the end of the study, participants’ beliefs about the treatment they thought they had received were collected. Both the subjects’ beliefs and the actual treatment had a dual effect on reducing inattention scores.

In the fourth study, 150 healthy participants got varying doses of tDCS for mind wandering. Those who believed they got a more potent dose reported more mind wandering, even if the actual treatment wasn’t a factor.

The fifth study analysed the impact of transcranial random noise stimulation on working memory. Here participants’ beliefs didn’t affect the results, highlighting the varying influence of beliefs in brain stimulation research.

“While you’d expect uniform improvements in a group of people with depression undergoing the same neurostimulation treatment, outcomes can vary widely,” Cohen Kadosh said.

“What’s truly eye-opening is that this variability could be largely influenced by the participants’ own beliefs about the treatment they’re receiving. In essence, if an individual believes they’re receiving an effective treatment — even when given a placebo — that belief alone might contribute to significant improvements in their condition.

“Our findings show that there could be real value in recording participants’ subjective beliefs at multiple points in the experiment to better understand their impact and put forward the importance of sharing this data and incorporating it within the research process.

“We may find similar results in pharmacological studies and more state-of-the-art interventions such as virtual reality, and I would encourage other scientists to use our analytical approach to re-examine results in past interventions and to incorporate it in future ones.”

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