What Is a Crossover Trial?

A crossover trial, also called a crossover study, allows researchers to evaluate how effective a treatment is. It is a clinical trial in which researchers compare two or more treatments by switching the subjects to another treatment as soon as they complete the first treatment. Subjects serve as their own controls.

Double-Blind

• Usually crossover trials are also double-blind studies. In double-blind crossover trials, researchers give their subjects a real treatment for a period of time and then switch them to a placebo. Each subject in the trial receives both the treatment and a placebo, which makes the trial a parallel-group design.

Advantages

• Researchers often struggle to find enough people for their studies. One advantage of a crossover trial is that it doubles the number of subjects in a given study, which in turn allows researchers to obtain statistically-significant results.

Disadvantages

• A major disadvantage with crossover trials is that subjects who take real treatments prior to placebos may see benefits during the placebo stage. It could be because of the real treatment's lingering effects or the power of suggestion. This makes crossover trials less reliable than standard trials.