wait-list control
a control condition in which the comparison group receives usual care while waiting to get the intervention after the trial — common where a placebo is impossible, and known to produce larger apparent effects than active controls.
you cannot give someone placebo psychotherapy. wait-list is the workaround, and it comes with a known bias worth naming.
what it is and why it exists
In drug trials the control group gets a matching placebo. For therapy, support programs, and services, there is nothing to disguise — so the control group simply continues usual care and is promised the intervention afterwards. This answers "is the program better than waiting?", which is a real question, but not "is it better than something?"
the known bias
Meta-research consistently finds wait-list comparisons produce larger effects than comparisons against active controls or even no-treatment without a promise. People on a wait-list know they are waiting, which can suppress improvement they might otherwise have found on their own. When this site reports a wait-list trial — the UPSIDES peer-support RCT is one — we name the design, because the effect size means something different than it would against an active comparator.
somewhere to put it
free. anonymous. people who’ve been where you are 🤍
get Resolv Social — it’s freewant the deeper story? read prescribed to fail
questions
does a wait-list design invalidate a trial?
No. It is often the only ethical, practical design for services research. It shifts interpretation: positive results say the program beats waiting, and the honest write-up says exactly that.
more from the glossary
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