Detectable vs. functioning are two different things. For cannabis, it is metabolites that are detectable for some time afterwards. They are no longer actively h

Detectable vs. functioning are two different things. For cannabis, it is metabolites that are detectable for some time afterwards. They are no longer actively having an effect on the person. These metabolites get deposited into some tissue, like hair or fat, and can be detected later. Imagine you eat cherries and accidentally stain your hair. This means that the cherry substance will be detectable in your hair for a long time, but any effects of you eating the cherries will be long gone.