"By making marijuana legal, you have more widespread use and many more health implications," Volkow said. "We don't need a third legal drug. We already have enough problems with the two we have."
The pro-marijuana advocacy group NORML agrees that pot "is not a harmless substance," Deputy Director Paul Armentano said.
"But its potential risks to the individual and to society do not warrant its present schedule I illicit status under federal law, a classification that improperly argues that the plant lacks any accepted therapeutic value and that its risks equal those of heroin," Armentano said.
Volkow is making her argument as the political winds continue to shift toward pot legalization.
Last week, the Republican-controlled U.S. House of Representatives voted in favor of preventing the federal government from interfering with states that allow marijuana use for medical reasons. Medical marijuana is legal in nearly half the states.
"Public opinion is shifting," Rep. Dana Rohrabacher, R-Calif., said at the time.
In the new article, Volkow and colleagues said marijuana is addictive, contrary to popular opinion. Research has shown that 9 percent of people who try pot will become addicted, she said. Pot's effect is even stronger among young people, addicting 17 percent of users under 18, she said.
"This is something that a lot of people who are pro-marijuana deny. The evidence shows otherwise," Volkow said.
Marijuana also poses a public safety risk. People intoxicated by pot are 3 to 7 times more likely to cause a car crash than someone sober, Volkow said.
Most troubling is the tendency for teens and young adults to use pot and alcohol at the same time, which increases the risk of a wreck more than if they used either drug on its own, she added.
Pot also appears to affect brain development in young users. Scans have shown that teenage pot users suffer from decreased brain activity and impaired connectivity between key brain areas, Volkow said.
"During adolescence, there is a tremendous amount of neuroplasticity," she said. "Regular use of marijuana is likely to have an adverse effect on the way the human brain gets connected and organized."
This may explain why frequent use by teens is linked to lower IQ and higher odds of dropping out of school, the report noted.
Volkow said other research has shown marijuana can:
Serve as a "gateway" drug.
Impair school performance.
Exacerbate mental illnesses such as schizophrenia.
Increase the risk of health problems such as chronic bronchitis and cardiovascular disease.
Legislators considering marijuana legalization should consider these effects, as well as all the gaps in current knowledge of pot's impact on human health, Volkow said.
"What is unfortunate in my view is that the information that's being presented is not objective. It's very subjective," she said. "We all want to think there is this drug that could make us feel relaxed and good with no harmful effects. That's a lovely fairy tale we all wish were true."
However, Armentano argues that "the ongoing criminalization of marijuana is a disproportionate response to what, at worst, is a health issue, not a criminal justice issue."
The adverse health consequences associated with alcohol, tobacco, and prescription drugs are far more dangerous and costlier to society than the responsible adult use of cannabis, he said. "It's precisely because of these consequences that these products are legally regulated and their use is restricted to particular consumers and specific settings," he said.
Legalization and regulation of marijuana will "best reduce the risks associated with the plant's consumption or abuse," Armentano said.
SOURCES: Nora Volkow, M.D., director, U.S. National Institute on Drug Abuse, Bethesda, Md.; Paul Armentano, deputy director, NORML; June 5, 2014, New England Journal of Medicine
Journal reference: Adverse Health Effects of Marijuana Use
Nora D. Volkow, M.D., Ruben D. Baler, Ph.D., Wilson M. Compton, M.D., and Susan R.B. Weiss, Ph.D. N Engl J Med 2014; 370:2219-2227June 5, 2014DOI: 10.1056/NEJMra1402309
Study Links Pot Use With Poor Sleep
. 04/06/14. It's possible that insomnia leads some people to turn to marijuana, study authors say. People who use marijuana may have trouble falling and staying asleep and feel drowsy during the day, new research suggests.
And adults who started using the drug before they were 15 seem to be twice as likely as nonusers to have problems falling asleep, not feeling rested after sleep and feeling tired during the day, the University of Pennsylvania researchers said.
It's possible that people who already suffer from insomnia turn to marijuana as a way to help them sleep, said study lead researcher Michael Grandner, an instructor in psychiatry at the university.
"The type of person who reports marijuana use in the U.S. is more likely to also be the type of person who has sleep problems," he said. "It doesn't mean that one is causing the other."
It's more likely that people with sleep problems and stress may turn to marijuana as a way to self-medicate, Grandner said. "But there is little evidence, outside of anecdotes, to suggest that this will really help fix the problem in the long term," he said.
Rather than turning to marijuana to beat insomnia, Grandner suggests trying treatments that really work.
"For example, the most well-studied treatment for insomnia actually does not involve medications and works well -- it's called cognitive behavioral therapy for insomnia and essentially works by reprogramming your brain to sleep," he said.
Since the study found that those who started using marijuana earlier in life were more likely to have sleep problems, it may be important to help teenagers find healthier and more effective ways to cope with stress, Grandner suggested.
The study didn't prove that marijuana leads to sleep problems, just that there's an association between the two. It was scheduled to be presented Wednesday at the Associated Professional Sleep Societies' annual meeting in Minneapolis.
For the study, Grandner's team collected data on approximately 1,800 U.S. adults who took part in the 2007-2008 National Health and Nutrition Examination Survey. The participants reported how often they had used marijuana in the past month and at what age they began using it. They also reported whether they had any trouble sleeping. The researchers defined severe sleep problems as trouble sleeping at least 15 days a month.
The strongest link between marijuana use and sleep problems was found in adults who started using the drug before age 15. They were about twice as likely to have severe problems falling asleep, the study authors said.
The debate about marijuana has been heating up as it has been legalized in two states and approved for medical use in others.
Study lead author Jilesh Chheda, a research assistant at the University of Pennsylvania's division of mood and anxiety disorders, said in the Sleep Societies' news release: "Marijuana use is common, with about half of adults having reported using it at some point in their life. As it becomes legal in many states, it will be important to understand the impact of marijuana use on public health, as its impact on sleep in the 'real world' is not well known."
The federal government lists marijuana as a "schedule 1 substance" that has no medicinal uses and is a high risk for abuse, according to the U.S. National Institute on Drug Abuse.
Two states, Colorado and Washington, have legalized marijuana for adult recreational use, and 21 states allow its use for certain medical conditions, such as cancer and glaucoma.
Paul Armentano, deputy director of NORML, a group that lobbies for the legalization of marijuana, said the "association reported in this paper of a history of cannabis [marijuana] use and severe difficulty falling asleep is relatively minor and it is questionable whether it holds any real world relevance.
"The ongoing criminalization of cannabis and those who consume the plant is a disproportionate response to what is, at worst, a public health concern -- not a criminal justice matter," he added.
Health concerns about marijuana, particularly its potential use or abuse by young people, are best handled by regulation, public education and age restrictions, "not by criminalization and stigmatization," Armentano said.
SOURCES: Michael Grandner, Ph.D., instructor in psychiatry, University of Pennsylvania, Philadelphia; Paul Armentano, deputy director, NORML, Washington, D.C.; June 4, 2014, presentation, Associated Professional Sleep Societies meet