Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Smoking Cessation Health Center

Font Size

Recreational Marijuana: Are There Health Effects?

Health Effects of Marijuana: Brain Impairment

Long-term, heavy use of marijuana can lead to impaired thinking skills and memory problems, Lamarine says, citing published studies.

The impairments can be especially hazardous when trying to do everyday activities such as driving.

However, these impairments appear to be most significant 20 to 40 minutes after using marijuana, then decline after an hour or so, Armentano says.

Individual reactions vary, of course. To be safe, he says, ''I think a three-hour window [between marijuana use and driving] is appropriate for [after] inhalation."

Lamarine says the effects may last longer than that. He says more research needs to be done for a definitive answer.

"I'd say three hours [between marijuana use and driving] is probably pushing it." However, he says, waiting three hours would be better than waiting less time, as he suspects many users now allow.

In a recent study, Yale University researchers looked at the effects of both marijuana and alcohol on driving. Both impair driving-related skills. But they found the impairment effects of marijuana, compared to those of alcohol, vary more among people.

That is thought to be due to differences in tolerance, smoking technique, and the potency of the marijuana.

While studies are conflicting about whether marijuana use alone leads to more accidents, combining it with alcohol definitely raises crash risks, experts say.

Health Effects of Marijuana: Mental Health

Numerous studies have linked marijuana use with schizophrenia. In this brain disorder, people may think they hear voices and that others are controlling their minds and thoughts.

However, Lamarine suspects the relationship may be reversed. "What I suspect is, people who are going to develop full-blown schizophrenia must feel bad beforehand," he says. They may be attracted to marijuana as a mood-altering drug to self-medicate.

If this link were cause and effect, Armentano says, the rates of schizophrenia would have climbed, as marijuana use has increased.

Marijuana use can be linked with anxiety, Lamarine and Armentano agree.

Several published studies, Lamarine says, have found a link between marijuana use and anxiety, but not necessarily full-blown anxiety disorders.

Studies have also found a link between regular marijuana use and panic attacks.

Today on WebMD

hands breaking a cigarette
Is quitting cold turkey an effective method?
14 tips to get you through the first hard days.
smoking man
Surprising impacts of tobacco on the body.
cigarette smoke
What happens when you kick the habit?

Filtered cigarettes
an array of e cigarettes
human heart
Woman experiencing withdrawal symptoms

man smoking cigarette
no smoking sign
Woman ashing cigarette in ashtray
chain watch