Support legal pot in Michigan? Know the latest health risks (and benefits)

Advocates of recreational marijuana legalization have reason to believe the drug will be approved by a popular vote come November. A majority of Michiganders tell pollsters they support legalization. But there are some known risks.(stock photo)

Update Dec. 4: You can smoke pot in Michigan but not buy it. What you need to know.
Nov. 6: Michigan approves recreational marijuana. What you need to know.

Cannabis is having its Cinderella moment. After decades of being the subject of social and political ire, it’s the belle of the ball.

Michigan is now poised to join nine other states and Washington, D.C. in legalizing recreational marijuana use for people over age 21. Polling suggests the initiative, put forth by the Coalition to Regulate Marijuana Like Alcohol, is likely to pass in November; 61 percent of Michiganders support it (only 35 percent oppose).

But not all health researchers are sanguine about the prospect.   

Judy Grisel, a behavioral neuroscientist at Bucknell University who studies drug addiction, told Bridge that some states are ignoring evidence of marijuana’s harmful effects, particularly on adolescent brains, in their eagerness to increase access.

“The risks certainly outweigh the benefits and the benefits are questionable,” she said. “We’re putting the cart before the horse to legalize it.”

Of course, in a sea of research filled with caveats and unsettled findings, Grisel’s views hardly represent a consensus. Claims about marijuana’s potential dangers and benefits abound. But which are true? Scientists tend to agree on some points — for example, that it can relieve pain, but can negatively impact mental health — and have called for further research on others, such as whether it’s a gateway to more dangerous drugs.

The U.S. Food and Drug Administration just approved the first drug made from marijuana on Monday, though experts say federal restrictions make studying the drug’s effects difficult. The National Academies of Sciences, Engineering, and Medicine, however, released a comprehensive report in 2017 calling for a national effort to address gaps in understanding how cannabis affects our bodies.

“We know little to nothing about edibles and other means of administration,” Aaron Carroll, a professor of pediatrics at Indiana University School of Medicine, recently wrote in the New York Times.

Bridge consulted the latest research and experts for this short guide to understanding marijuana’s effects. Below are some findings the National Academy lists as having conclusive, substantial or moderate evidence — in other words: conclusions with “very few or no credible opposing findings.”

Health benefits

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Perhaps marijuana’s most well-known physical benefit is treating chronic pain. The National Academies identified five reliable studies that indicated cannabis is helpful for reducing pain for a variety of ailments such as arthritis and cancer-related pain. Experts also say this benefit could provide a way to combat the opioid epidemic — both recent and older studies show significant reductions in opioid use in states where marijuana is accessible, though other studies suggest  legal access to marijuana does not cut down on opioid-related overdoses.

(stock photo)


This week, the FDA approved Epidiolex, the first-ever drug derived from marijuana that is used for treating seizures associated with two rare forms of epilepsy that begin in early childhood. The active cannabis ingredient is CBD ‒ a component of cannabis that is not associated with marijuana’s psychoactive effects from THC ‒ which was shown to reduce the frequency of seizures. A 2016 study also indicated CBD would be helpful for treating seizures in these treatment-resistant forms of epilepsy.

(stock photo)


Cannabinoid treatments have been effectively used for treating nausea for more than three decades, primarily among chemotherapy patients who can experience intense nausea and vomiting as a side-effect of their treatment. Several studies show cannabinoids taken orally (by pill, rather than inhaled) are as effective as leading prescription drugs. The National Academies wrote there is also “an abundance of anecdotal reports” that smoking or eating plant marijuana is also helpful for nausea, but “existing obstacles” have gotten in the way of fully investigating it as a treatment.

(stock photo)


There is some evidence to suggest cannabis can improve sleep in the short-term for people with sleep apnea or pain from conditions like fibromyalgia or multiple sclerosis.

Preliminary research reviewed in a recent study also indicates that CBD may be helpful for treating insomnia. THC, in contrast, may help people fall asleep in the short-term but could harm sleep quality in the long-term. Experts agree that more research is necessary to fully understand marijuana’s effect on sleep.

Health dangers

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Mental health

For those with a mental illness, there’s significant reason to consider avoiding cannabis. Several high-quality studies show marijuana is linked to an increased risk of developing schizophrenia and other psychoses ‒ “the higher the use, the greater the risk,” the National Academies wrote. Conversely, those who already have schizophrenia and have used cannabis in the past (but not recently) may learn and remember more effectively.

Cannabis users are more likely to become depressed. Heavy pot smokers are more likely to develop social anxiety and, more alarmingly, contemplate, attempt and complete suicide. However, it’s hard for scientists to show direct causality — that marijuana is the cause of these problems — based on existing studies. People with bipolar disorder who smoke weed regularly may also experience more frequent manic episodes.

(stock photo)

Lung performance

The National Academies found “substantial” evidence of an association between regularly smoking pot and worsening respiratory symptoms, which vary from more frequent bronchitis to more coughing, wheezing and phlegm than non-users. Three studies indicate that stopping smoking marijuana can improve symptoms. One suggests that using a vaporizer rather than smoking joints could also help.

What scientists define as “regular use” varies — some studies of cannabis users included those who smoked around once a week, while others considered included those smoking at least once a month.

A 2007 systematic review found that smoking weed actually increases airflow in the lungs in the short term, but any benefits could be offset by a 16 percent reduction in airflow for long-term, regular pot smokers.

(stock photo)

Car crashes

The National Academies found substantial evidence of a relationship between marijuana use and an increased risk of car crashes. The most comprehensive one they looked at showed a 20 to 30 percent relative increase (a “low to medium magnitude” change, according to the report) in car crashes associated with short-term cannabis use.

More recently, a study conducted by the Insurance Institute for Highway Safety found that insurance collision claims increased by 3 percent in states that legalized marijuana. However, another study published in the American Journal of Public Health found that fatal car accidents were not more frequent in Washington and Colorado than in similar states without legal recreational marijuana, and another study even found a decrease in the number of people killed in car accidents in states that legalized medical marijuana. You can read an analysis of two of those studies’ methodologies here.

These are complicated findings. Cannabis users often share many of the same characteristics as those likely to be involved in car crashes — for example, being young, male and someone who has a tendency to drive drunk are all demographics common among those who smoke weed and those who get in car crashes — so experts say it’s tricky to figure out how cannabis alone affects the likelihood of an accident. Plus, we still don’t have a breathalyzer-like tool for detecting marijuana.

(stock photo)

Adolescent cognitive functioning

Studies show that those who have recently used cannabis (within 24 hours) are worse at learning, remembering and paying attention. However, there’s little data to show that this persists over time — as of now, once you stop using, there’s reason to believe you’d return to normal brain functioning.

The thing that scares scientists is the possible effects on the adolescent brain. There isn’t sufficient research to come to concrete conclusions, but data in existing systematic reviews indicate that the earlier people start smoking pot, the greater their impairment as an adult.

“There’s a good dose-response relationship. The more you take, the more changed the (neural) circuits are,” said Grisel of Bucknell University.

Research shows cannabis can affect memory, learning and impulse control for those who start using heavily as teenagers. Other studies show adults score lower on IQ and verbal tests if they began smoking frequently as teens.

These findings are not bulletproof ‒ many studies were done on rats (which have much shorter periods of adolescence than humans), and results from human studies can be clouded by other environmental factors that influence brain development. But scientists agree that the dangers are alarming enough to warrant further study, such as this forthcoming 10-year study from the National Institutes of Health.

(stock photo)

Low birth weight

Children whose mothers smoked marijuana while pregnant with them are more likely to be born at a lower birth rate, which can lead to both short- and long-term complications. One reason for that is increased exposure to carbon monoxide, which “may be up to fivefold higher after marijuana than cigarettes,” according to the National Academies.

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Wed, 06/27/2018 - 8:57am

I hope that if we allow marijuana usage, that we also consider excluding certain activities like driving when using. Is there something equivalent to a breathalyzer for law enforcement to use? What should the limit be? I don’t care what a person does to themselves in the privacy of their own homes, but when they affect others, it should have consequences. It hurts to read stories like a drunk driver plowing into a pedestrian, biker, or road worker.

Thu, 06/28/2018 - 1:41pm

According to the article there is not currently any testing method similar to a breathalyzer used in detecting alcohol conzsumption.

GD Ann Arbor
Wed, 06/27/2018 - 9:10am

A taxpayer and non-user's perspective: Article fails to mention cost and risks of enforcing current marijuana laws as detrimental to health and wellbeing.

Wed, 06/27/2018 - 9:23am

If illegal and unregulated pot is easier to get than alcohol, as it frequently is, I suspect that it actually increases adolescent use because they will try to find something to use. The fact that we can't actually study pot or guns is scary. Ignorance for some seems to be bliss. In a free society, adults should be free to make their own choices, and scientists should be free to look for solutions to society's problems. On this ballot, we can fix one problem, and hopefully another.

Trout River
Wed, 06/27/2018 - 9:39am

I think this will pass because many people are tired of the police and courts ruining citizens lives because of possession of MJ. This article did not discuss how criminalization has cost society billions of dollars in enforcement, prosecutions and jail time for a drug less dangerous than alcohol. Several of the dangers cited above would also appear in an article on the dangers of.......sugar.

Wed, 06/27/2018 - 9:51am

What all these equivocal findings seem to indicate is that whatever the risks are of marijuana use, and surely there must be some as every drug has side effects, they must not be extreme and easy to identify. I wish the conventional pharmaceutical products were subject to the same degree of scrutiny -- we would have probably stopped the opioid epidemic sooner.

Susan Bender
Wed, 06/27/2018 - 9:59am

Legalizing today's marijuana (can't be compared to what we smoked before commercial production) is akin to re introducing alcohol and tobacco to society in the day that medical interventions were only loosely based on scientific inquiry. Have we established the legal parameters for driving while under the influence? Are we the least bit ready for the consequences - legal, medical and social - of a decision made without reference to much data. Some European countries have established legal limits for DUI, but these parameters were chosen out of practical necessity since there is not a linear relationship between measurable blood levels and the degree of impairment. This is all just a political strategy to keep taxes down. But the same politicians who vote to prevent union wages (wealth creation ) think this is a better way to increase the tax base?

John S.
Wed, 06/27/2018 - 10:05am

Thank you for this post, especially the evidence based on the NAS report. As many have said, cigarettes are far worse than marijuana. I'd add that THC likely evolved as a natural pesticide. It's a poison.

Robyn Tonkin
Wed, 06/27/2018 - 10:13am

De-criminalizing marijuana is about getting law enforcement and the courts off of peoples' backs about it. It's about making money growing it. I buy plant starting supplies online, and the sellers are not about growing flowers and vegetables anymore- they're all about selling stuff to grow marijuana. Big Pharma has conditioned people to want to take something for everything about the human condition. Ever read the caveats listed in magazines in conjunction with drug ads? The list of side effects ranges from the daunting to the terrifying. But people keep getting prescriptions filled. What people want to do is gaze at their smartphone whilst high on something, whether it's beer, booze or marijuana. Why should law enforcement manpower and money be tied up attempting to circumvent this tedious relationship?

Erwin Haas
Wed, 06/27/2018 - 11:11am

Marijuana is illegal everywhere; it can't be studied until it can be tested in good double blinded, controlled trials; the various claims made in this article are “conjectures that wear an aspect of probability” to quote someone.
The problem is one of selection bias, just like the claim that finishing High School or college will make someone richer. The folks who use this stuff are different from those who never used and don't intend to use; they may be more adventuresome, maybe mentally slower with different brain structure, maybe depressed and so indulge.
I support the legalization of Marijuana for two reasons; its use can be studied in a proper "scientific" way and, after it is normal to grow crops of this cannabis we can grow the more interesting and profitable hemp plant here in the 26th senate district. It can be a game changer for our farmers.

Chuck Fellows
Wed, 06/27/2018 - 11:57am

Interesting how all these conclusions have been reached without any serious study being done because the politicians (AKA Drug company sycophants) will not allow it - they control the funding for these kinds of studies for schedule 1 drugs. "The committee notes that there were several challenges to conducting the review, including regulatory barriers such as classifying cannabis as a Schedule I substance. The report found that these barriers are impeding the advancement of research of the effects of cannabis use. "

Wed, 06/27/2018 - 7:55pm

Yes, funny how weed and guns cannot be studied - esp. because of Republicans. Wonder why... could it have something to do with lobby money and bribes, er, 'campaign contributions'?
Kind of like when I urged Snyder and others to at least review and study if tax cuts produced jobs and to create mechanisms in the massive tax cut here in MI to track if jobs were actually created. Nope - quite the opposite. It was made impossible to track jobs and tax cuts. Just throw out $2 billion in tax revenue and hope.

Wed, 06/27/2018 - 7:36pm

After reading some of the comments here I assume paranoia is a side effect.

Paul Jordan
Wed, 06/27/2018 - 8:29pm

I haven't smoked--or been tempted to smoke--marijuana for well over 40 years. I am not an advocate of marijuana.
Based upon this article, though, it seems as if marijuana has more potential to help people than alcohol ever has. The legal status of alcohol for adults is not based upon the healthfulness of alcohol use. It is based upon the fact that making alcohol illegal did nothing to reduce the use of alcohol.
It is the same with marijuana. Ending the criminalization of marijuana is NOT an endorsement of the use of marijuana! It is simply an acknowledgement that treating the sellers and users of marijuana as criminals has caused tremendous harm without any reduction in the use of marijuana.
Through the criminalization of marijuana, we have been digging a hole that has destroyed lives, wasted public treasure, and benefited nobody. It is only common sense under these circumstances for us to stop digging this hole. It is (past) time to treat marijuana like alcohol.

David Richards
Thu, 06/28/2018 - 11:45am

Someone is concerned about "increased access"? It seems to me there is plenty of access now, and that access is usually through low-life drug dealers, a far greater danger than legal regulation. Whether marijuana is good or bad, it is available now. The question is what is the optimum way of dealing with it. Our prohibition laws have been no more effective than they were with alcohol.

Mrs A
Thu, 06/28/2018 - 6:14pm

How can any study claim to have achieved a defensible result on a substance still included on Schedule 1 and therefore ineligible for any study? (Though scientists in Israel and other nations are making significant testing progress.) The LD-50 (lethal dose to 50% of test subjects, a measurement of toxicity) of cannabis sativa/indica is virtually zero, unlike alcohol, tobacco and a host of other legal drugs. In other words, chugging a quart of vodka would likely kill you, but smoking 100 blunts would not (even if you could stay awake beyond the second or third.) Let us always remember that BEER, not cannabis, is the gateway drug.

Sat, 03/16/2019 - 7:54am

There are so many people, now in their 50's and 60's, who started smoking in their teens. Nobody that I know in this category will tell you that it has caused depression, car accidents, less ability to function through memory, IQ, etc. In fact, most of these people are professionals who function very well. None and I repeat, NONE of them have gone on to "harder" drugs, and most of them who tried harder drugs when they were in their teens and twenties went back to pot and ceased using anything else. Of course there are situations where one shouldn't use pot, just as there are situations where one shouldn't use alcohol, caffeine, sugar, etc. , but I have to wonder how they are conducting these studies and who they are actually dealing with. There is a wealth of long term effect information out there if anyone were to ask.