How Long Does Marijuana-Induced Impairment Actually Last

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Marijuana’s legal status in more than three dozen states has given rise to a whole host of questions in desperate need of answers. One such question is this: how long does marijuana-induced impairment actually last? We need to know the answer sooner, rather than later. Why? Because millions of people now use marijuana both recreationally and medically.

We already know that marijuana impairs cognition, motor function, and response times. We also know that THC, the cannabinoid in marijuana that makes people high, can remain in a person’s system for weeks after consumption. But having THC in one’s system does not make a person high. THC in the system does not equate to impairment.

Marijuana joint in
Marijuana joint in the hand, Concepts of medical marijuana use and legalization of the cannabis.

People Respond to Marijuana Differently

One of the more interesting aspects of marijuana and its ability to impair is the fact that people respond to it differently. In fact, varying responses is one of the fundamental truths of medical cannabis consumption. THC is like any other drug in the sense that it doesn’t always have the same effect on every patient.

At, medical providers help patients obtain medical cannabis cards. They also advise patients in the best ways to use medical cannabis to treat their respective conditions. A piece of advice they give to all patients is to track their cannabis consumption. Tracking provides data that patients and pharmacists can use to improve treatments.

The truth is that medical cannabis patients respond differently to delivery methods, dosage, and even medical cannabis products themselves. Why would we expect anything different where recreational marijuana consumption is concerned?

Many Things Affect Response

A whole list of things can influence how a person’s body responds to marijuana. For starters, you need to consider delivery method. Smoking is the most utilized delivery method among recreational users for one simple reason: the practice gets THC into the bloodstream almost instantaneously. Smoking is the fastest way to get high. However, the effects of smoking marijuana are short-lived compared to other delivery methods.

Take marijuana edibles. It could take two or three hours for the effects to be felt. But once a person starts feeling high, those feelings last longer because it takes longer for the THC to completely work through the person’s system.

Other things that can influence response include:

  • the amount consumed
  • a person’s weight, sex, and age
  • underlying medical conditions
  • the use of other drugs.

The list goes on and on. We can generally say that consuming THC will make a person high. But that is about as far as we can go. The details of how a person actually feels, and how long they feel that way, differs from one user to the next.

Tolerance Also Plays a Role

Tolerance is another key factor. According to Psychology Today contributor and marijuana expert Gary Wenk Ph.D., long-term marijuana users develop tolerance. This is to say that their response to THC decreases over time. They need to use more to enjoy the same level of enjoyment.

Wenk cites a number of studies suggesting that impairment times decrease commensurate with the length of time a person has been using marijuana. That makes sense given the tolerance issue. The longer a person uses marijuana, the shorter the amount of time they are impaired by it.

We have reached the point at which marijuana consumption is commonplace. With that being the case, it is now more important than ever that we understand how long marijuana-induced impairment lasts. Failing to answer that question will prevent us from updating laws and policies related to impairment. And that will only lead to more problems.


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