DO NOT PUBLISH How do we know what works?

Randomised controlled trials (or RCTs) are the current best method we have for finding out what interventions work; in medicine and in psychological therapy. Even though they sound fancy, RCTs work in a really obvious way: separate people into two group who are similar in every way EXCEPT that one gets the intervention, and the other doesn’t. Measure the same symptoms/outcomes in both groups in the same way, and then we can say that any difference between them is because of the intervention and not due to other reasons. This works when comparing two treatments to each other too..

Other reasons might not be so obvious; sometimes people just get better, when measuring a group the group always tends to even out around the middle over time, so statistically it is likely that groups look like they are improving…Often people knowing what treatment they’re getting influences their improvement. This has been seen by the placebo effect, when people taking a drug with NO chemicals improve simply because they think they are getting a treatment. Blinding is therefore important, to make it so both groups think they are getting the treatment. Double blinding means that neither the patient or the researcher know who is getting the drug or not, as even this knowledge can effect how a person reports their improvements.

In RCTs of psychological therapy it is not possible to blind people, indeed, most therapies rely on the person taking part to be involved and engaged with it to work. Most psychological trials compare interventions to each other, or to a waiting list control group. Using these methods we can reliably show that psychological interventions can help people with a wide variety of mental health difficulties. At the moment however, there is little agreement on what adverse (side) effects should be measured in RCTs, or indeed, what they are. In medical studies outcome measures of side effects are used to compare the bad effects of drugs, so people can make informed decisions of which treatment they want to try. We want to create a similar measure for psychological therapies, and we need your help to do it.