Hazard ratio

A hazard ratio compares how quickly an outcome happens in one group versus another over time. It's about timing, not only whether something happens.

This term is specific to research interpretation and is defined on AnxietyResearch. Shrinktionary, the network's language layer, doesn't currently carry a canonical entry for it.

Relative risk asks whether an outcome happened by the end of a study. A hazard ratio asks how fast it happened along the way. It comes from studies that track the time until an event, such as a relapse. A hazard ratio of 1 means the same speed in both groups. Below 1 means slower. Above 1 means faster.

Hazard ratios appear in studies of relapse and of staying in treatment. A study might report how long people stay well after finishing therapy, and whether one treatment delays relapse longer than another.

A study of relapse after anxiety treatment reports a hazard ratio of 0.6 for people who continued medication. Continuing treatment was linked to a slower rate of relapse over the follow-up period.

A hazard ratio describes a rate over time, not a simple final count. It assumes the gap between groups stays roughly steady across the whole follow-up, which isn't always true. As with other ratios, check the confidence interval.