No-one likes waiting their turn, but according to a new study, just knowing that you’re ‘on a waiting list’ could change your behaviour: Exploratory randomized controlled trial evaluating the impact of a waiting list control design
The research was conducted by an Canadian team led by John A. Cunningham, and it made use of a beautiful experimental design.
The participants were 185 people who wanted to cut down on their drinking. They’d volunteered for a trial of an ‘intervention’ to help them do it. The volunteers filled out an alcohol use questionnaire, and were then sent a letter with feedback based on their answers.
Here’s the clever bit – the participants were randomly assigned to two groups.
One group were told that they were on the waiting list to get the treatment, and that the feedback was a standby:
You are in the waiting list condition of this study. You will need to wait for 4 weeks until we can send you the intervention materials. In the meantime, we have generated some personalized information about your drinking and it is included with this letter.
While the other group were told that the questionnaire and feedback they’d got was the promised treatment.
You are in the intervention condition of this study. We have developed a personalized feedback intervention for people concerned about their drinking. We generated a Final Report for you from this intervention and it is included with this letter.
What happened? Four weeks later, when participants completed a second questionnaire about their recent drinking, it emerged that those in the ‘intervention’ group were more likely to report having cut down their drinking to a healthy level (“Fisher’s Exact test, p = .03; told intervention condition = 27.6 %; told waiting list = 13.6 %”).
It makes sense. Everyone who entered the trial wanted to cut down but felt they needed help – so, naturally, they would wait until they perceived that help was at hand to try and make the change.
Some of the other outcome measures were a bit less impressive, but it’s a very elegant design, which allowed Cunningham et al to directly measure the effects of the idea of ‘getting an intervention’ (or not) independent of the actual intervention itself.
In my view, this approach should be used more widely.
It could work with other interventions such as computerized psychotherapy, brain-training programs, self-help books and more. All of these have been shown to be much more effective than a waiting list, but how much does that really tell us?
This technique could help to distinguish between specific treatment effects and nonspecific factors that make people (report being) better e.g. the placebo effect, experimental demand biases, and expectations.
Cunningham JA, Kypri K, & McCambridge J (2013). Exploratory randomized controlled trial evaluating the impact of a waiting list control design. BMC Medical Research Methodology, 13 (1) PMID: 24314204