When people call something the "gold standard" of evidence, they usually mean the randomised controlled trial.
In the search for evidence that a treatment really works, one study design stands above the rest for a single well-run comparison: the randomised controlled trial, or RCT. This post explains what an RCT is, why it is so trusted, where it has honest limits, and what it means for hypnotherapy.
It is part of our short series on the science of hypnotherapy, alongside why evidence matters, how to read a scientific paper, how to understand research results, and where to find the journals.
What is a randomised controlled trial?
An RCT is a study designed to test whether an intervention actually causes an effect. Participants are randomly assigned either to a treatment group, which receives the intervention, or to a control group, which receives a placebo, a comparison treatment, or no intervention. The outcomes of the two groups are then compared.
In hypnotherapy, RCTs are used to test techniques and approaches for issues such as anxiety, depression, pain management and smoking cessation.
The two foundations: randomisation and control
Two principles make the RCT so powerful.
Randomisation means assigning participants to groups purely by chance. This tends to spread known and unknown differences evenly across the groups, so that the only systematic difference between them is the treatment itself.
Control means having a comparison group that does not receive the intervention. Without a fair comparison, you cannot tell whether people improved because of the treatment, or because of time, attention, or the placebo effect.
Together, randomisation and control let researchers isolate the effect of the intervention.
Why the RCT is called the gold standard
- It reduces bias. Random assignment guards against the treatment and control groups differing in ways that could distort the result.
- It supports claims about cause. Because the groups start out comparable, a difference in outcomes can more confidently be attributed to the intervention.
- It accounts for the placebo effect. A control group receiving a placebo or usual care helps show that improvement is due to the technique, not simply the expectation of help.
- It can be replicated. A clearly described trial can be repeated by others, and replication is how confidence is built.
One important caveat: a single RCT is not the top of the evidence pyramid. Systematic reviews and meta-analyses, which pool many trials, sit above any one study, because a conclusion supported by many trials is stronger than one supported by a single trial.
Strengths in hypnotherapy research
RCTs bring particular benefits to a field like hypnotherapy, where experiences are subjective and expectations run high. They use standardised outcome measures, allow different techniques to be compared head to head, and produce the kind of robust evidence that builds credibility with other health professionals.
Honest challenges and limitations
RCTs are demanding, and in hypnotherapy they carry some specific difficulties.
Cost and complexity. Good trials are expensive and slow, which limits how many are done.
Ethical limits. It is not always acceptable to withhold a promising treatment from a control group, especially for serious conditions.
Blinding is genuinely hard. In drug trials, neither patient nor clinician need know who received the real pill. In hypnotherapy, both the client and the therapist usually know that hypnosis is being used, which can let expectation influence the result. Careful design, such as using independent assessors who do not know which group a participant was in, helps but does not fully solve this. Trials that follow the CONSORT reporting guidelines make these design choices transparent, so you can judge how well they were handled.
Frequently asked questions
What makes an RCT the gold standard?
Randomisation and a control group let researchers isolate the effect of a treatment and support claims that it actually caused the observed change, while reducing bias and accounting for the placebo effect. That combination is hard for other single-study designs to match.
Is a randomised controlled trial always the best evidence?
For a single study, it is the strongest design for testing whether a treatment works. But a systematic review that combines many good trials is stronger still, because it reflects the weight of the evidence rather than one result.
Why is blinding difficult in hypnotherapy trials?
Because both the client and the therapist usually know that hypnosis is being used, expectations can shape the outcome. Researchers reduce this by using independent, blinded assessors and standardised measures, but blinding is harder here than in a typical drug trial.
Does the difficulty of running RCTs mean hypnotherapy is unproven?
No. It means some techniques are under-researched rather than disproven, and that we should weigh the evidence that does exist carefully. See what hypnosis can help with for a condition-by-condition look at the evidence.
Keep building your research literacy
At Jacquin Hypnosis Academy we want practitioners who can weigh the evidence for themselves. Continue with the rest of this series: why evidence matters, how to read a scientific paper, how to understand research results, and where to find the research. You can also trial our training platform free for 14 days.