Clinical trial

A clinical trial is a research study in which people receive an intervention under a written protocol so that its safety and effects can be measured.

Trials progress through phases: phase 1 tests safety and dosing in a small group, phase 2 looks for a signal of effect in people with the condition, and phase 3 compares the intervention with placebo or standard care in a larger population to support regulatory approval. The strongest design is randomized, double-blind and placebo-controlled, meaning participants are assigned by chance and neither they nor the investigators know who received the active product until the study ends. Ethics review, informed consent and registration in a public database are required before enrollment begins.

In cannabinoid science, a handful of large trials support the approved uses of purified cannabidiol for rare seizure disorders, while most other claims rest on small trials, open-label studies, surveys or animal research. When a glossary entry says a use has been studied, it usually means such preliminary work exists, not that a phase 3 trial has succeeded.