Dichotomizing rating scale scores in psychiatry: a bad idea?

In psychiatry, the use of rating scales as measures of outcome in clinical trials allows us to generate continuous outcome data, where each individual's outcome is measured in numbers. Continuous outcomes can be divided into two categories, such as improved and not improved, or may be kept continuous. This article briefly presents the main advantages and disadvantages of these two approaches, which are commonly employed in the analyses of rating scale scores in clinical trials and systematic reviews.