there is some good info here:

Marijuana: Effects of Weed on Brain and Body

For the purposes of your story it could relax someone as it effects the same neurological centres that etoh and heroin do by releasing dopamine. But it can make people anxious and paranoid too, if you wanted to go that way with it. it can heighten sensory perceptions too, with colours brighter etc etc and can cause hallucinations. for the purposes of f your story ingesting it in cookies etc is quite unpredictable, both I terms of the effects from the dose and also when the effects occur, smoking or vaping would be easier to control both the size of he dose and the timing of the effects.