WebMD Health News
Dec. 11, 2012 --
On Monday, Colorado Gov. John Hickenlooper signed an order legalizing recreational
marijuana use for adults.
Last week,
Washington was the first state to OK adult recreational use of the
drug. Several other states are considering similar laws.
While much research has focused on the value of medical marijuana to help chronic
pain and other problems, what about the health effects of purely recreational marijuana?
WebMD turned to two experts, recently published
studies, and the National Institute on Drug Abuse to draw up a scorecard
of possible major health effects.
Health Effects of Marijuana: Lungs
"Putting smoke in your
lungs
is not good for the lungs," says Roland Lamarine, HSD, professor of
public health at California State University, Chico. He reviewed
published studies on the health effects of marijuana earlier this year
for the
Journal of Drug Education.
Smoking
marijuana produces a nearly threefold increase of inhaled tar compared
with tobacco, according to some studies. Other research suggests that
marijuana smokers, compared to cigarette smokers, inhale more deeply and
hold their breath longer.
"There are still questions that aren't answered
about lung damage," Lamarine says. For cigarette smokers who also smoke
marijuana, there may be an additive effect, he says.
Combining the two appears to be a trend, he says. "Some of the [college] kids tell me they buy
cigars and put in some marijuana, so there is both marijuana and tobacco," Lamarine says.
Marijuana smoke contains
cancer-causing
substances, according to the National Institute on Drug Abuse. Some
research shows that marijuana smoke has up to 70% more cancer-causing
substances than tobacco smoke, it says.
"Nobody is advocating that routinely inhaling
carcinogenic smoke is healthy," says Paul Armentano, the deputy director
of NORML (National Organization for the Reform of Marijuana Laws).
However, he says, many marijuana users these days
have turned to alternate delivery methods, such as oral, tinctures, and
vapor forms. In research, he says, the vaporized forms have fewer
adverse chemicals than the inhaled form.
Those who keep marijuana use light do not appear to lose lung function, according to a 2012 study in the Journal of the American Medical Association.
Researchers compared tobacco and marijuana users.
Tobacco use was associated with lower lung function, and the function
got worse as smoking levels increased.
For the study, low levels of lifetime exposure to
marijuana, defined as one joint a day for seven years, did not show
evidence of adverse effects on lung function. The study does not confirm
these findings with heavy users.
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.
Some marijuana users do have panic attacks, especially if they are new to the drug, Armentano says.
As for the anxiety-marijuana link, he says, it could be that some anxious people try marijuana to self-medicate.
Those who have known psychotic problems should proceed with caution when thinking about marijuana use, Armentano says.
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