It’s long been recognized that the gold standard in medical drug research is a randomized, placebo-controlled study. While not without its faults, this type of research ensures that the drug being tested is more effective (and just as safe) as a pill that contains no active ingredients. That way, the data can show that secondary effects — such as the act of taking a pill once a day or seeing a doctor for refills or collecting study data — aren’t the main cause of any benefits the research may find.
In psychotherapy research, there is no pill. So a long time ago, some researchers developed what they believed to be a similar control group as those receiving a placebo — the waitlist control group. The wait-list control group is simply a group of subjects randomized to be placed on a fake “waitlist” — waiting for the active treatment intervention.
But there are more than a few problems with this type of control group in research. In a word, waitlist control groups suck.