A: The window of impairment is the length of time a person is negatively affected “high” from marijuana’s (THC) psychoactive properties. The latest science demonstrates significant impairment for up to 4.5 hours following smoking of cannabis. Other studies have shown the window of impairment can be as long as 12 hours depending on the task measured, the amount of THC consumed, the method of THC consumption, the frequency of consumption, as well as physiological differences between participants. (11-17)
