The effect from smoking pot generally affects users immediately, but also begins to diminish immediately. Marijuana edibles take longer to start working — usually 30 to 60 minutes. However, the effects can last between 4 to 12 hours depending on the dose. Edibles are often a preferred method for ingesting cannabis because of the negative impact smoking has on one’s health. Additionally, edibles can be discreetly consumed in places where smoking is not allowed.