The waitlist control group serves two purposes.
First, it provides an untreated comparison for the activeexperimental groupto determine if the treatment had an effect.
Second, it allows the wait-listed participants an opportunity to obtain the intervention at a later date.
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At a Glance
In an experiment, some people may be randomly selected for the waitlist group.
They also closely resemble the participants in the experimental group (or the individuals who receive the treatment).
While participants in this group do not immediately receive the treatment, they do eventually.
Any differences between the two groups are therefore the result of the manipulations of the independent variable.
Prevalence
The use of waitlists in psychotherapy research is common.
According to one study, around 73% of published psychological treatment studies rely on waitlist controls.
However, the researchers note that this bias can vary depending on the study population.
In some cases, the condition of patients on the waitlist may decline when treatment is delayed.
Such groups allow participants to access an intervention, although treatment might be delayed.
Waitlist control groups can be useful, but they can also have some downsides.
Wait times may have an impact on intervention effects.
American Psychological Association Dictionary of Psychology.APA Dictionary of Psychology: wait-list control group.
2012;19(3).
Cochrane Methodology Review Group, ed.Cochrane Database of Systematic Reviews.
2022;2022(4).
