Glossary · Methodology
Double-blind
In short
Double-blind means that neither the participants nor the investigators know who receives the active ingredient and who receives the placebo. That way, expectation cannot colour the result on either side.
People who know they are getting the real substance often feel better; doctors who know who is being treated unconsciously measure and ask differently. Both shift results — most strongly for complaints that people rate themselves.
A trial is single-blind if only the participants do not know, and open-label if everyone knows. Some things cannot be blinded at all, such as a sauna session or an ice bath. Then the uncertainty stays larger, and that belongs in an honest assessment.
If a substance has noticeable effects, such as tingling or skin flushing, many participants guess which group they are in. Good trials ask at the end how well the blinding held.
If you do not know what you are getting, you cannot talk yourself into it.
Where this comes up in the fact checks
- Finasteride – The hair counts come from blinded trials with 1,553 men — one reason why the finding holds up.
- Sauna & cold – Heat and cold cannot be blinded; the strongest numbers come from an observational cohort.
- Therapeutic plasma exchange – A blinded trial with a sham treatment: after six sessions, no difference in the ageing clocks was measurable any more.
Sources
Related terms: Placebo · Nocebo · Randomized controlled trial (RCT)
Information only, not medical advice. The BK-Score is a subjective assessment according to disclosed rules – not a scientific evaluation. Scoring rules