A trial in which the subjects receive, in sequence, the treatment (or control intervention), then, after a specified time, the control intervention (or treatment).
Note: In this type of study, the subjects are their own controls, and randomisation is used to determine the order in which a subject receives the treatment and the control intervention. Washout periods are usually included, since otherwise the effects of the first treatment could carry over into the period when the second is given.
Syn.: crossover study