Randomized controlled trials: randomize, control, blind
Explains the three design features that let a randomized controlled trial (RCT) show a drug works — randomization, a placebo control and double-blinding — and the ways real trials fall short.
Where this fitsConnects to 2 · Unlocks 2
- Connects to
- Primary effects and side effects — Trials are how side effects are separated from coincidence.
- The course lens: biopsychosocial, and no 'chemical imbalance' — The psychological part of the biopsychosocial lens is what placebo controls account for.
- Unlocks
- Expectancy: placebo and nocebo effects — Why expectancy is powerful enough to need a placebo group.
- Phases of drug trials: from animals to Phase IV — RCTs are the core of Phase III.
Orient
Randomized controlled trials are “the ‘gold standard’ of clinical research”: randomized – random selection and assignment to groups, including double-blind; controlled – compare “drug” group with “control” group(s). For a drug to be considered effective, outcomes must improve BEYOND what is seen with sham. Why do we need to do this? Expectancy effects.
Course terms
Your professor's wording, word for word from the slides. Learn the term and this definition — the explanation underneath is only there to help it make sense.
- Randomized controlled trial
“The “gold standard” of clinical research”Slides 07, p. 2
Its experimental design allows claims about causality: the drug is causing the beneficial effect.
- Randomized
“Randomized – random selection and assignment to groups”Slides 07, p. 3
Chance decides who gets the drug, so the groups start out alike.
- Double-blind
“participants and clinicians don’t know who is in what group”Slides 07, p. 3
Blocks the expectations of both sides from tilting the results.
- Controlled
“Controlled – compare “drug” group with “control” group(s)”Slides 07, p. 3
Arms can get the drug (possibly at different doses), nothing (pure control) or a sham such as a sugar pill.
- Placebo run-in
“every patient is administered a placebo for a week”Slides 07, p. 10
Patients who respond positively are removed from the study — which raises the question of who is left.
- Open-label study
“In open-label studies, there is no blinding – participants (and clinicians) know that they are taking a drug or a placebo…openly!”Slides 07, p. 11
Placebo effects still appear, through the conditioned ritual of taking a pill.
From your course: Course slides 07, pp. 2–3, 10–11, 17–22 · Midterm study guide: Clinical Trials and Policy
Tip: the ← and → keys move through the lesson.