Do Probiotics Work For Weight Loss?
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It’s Q&A Day at 10almonds!
Have a question or a request? We love to hear from you!
In cases where we’ve already covered something, we might link to what we wrote before, but will always be happy to revisit any of our topics again in the future too—there’s always more to say!
As ever: if the question/request can be answered briefly, we’ll do it here in our Q&A Thursday edition. If not, we’ll make a main feature of it shortly afterwards!
So, no question/request too big or small
❝Can you talk about using probiotics for weight loss? Thanks❞
Great question! First, a quick catch-up:
How Much Difference Do Probiotic Supplements Make, Really?
Our above-linked article covers a number of important benefits of probiotic supplements, but we didn’t talk about weight loss at all. So let’s examine whether probiotics are useful for weight loss.
Up-front summary: the science is unclear
This 2021 systematic review found that they are indeed very effective:
❝The intake of probiotics or synbiotics could lead to significant weight reductions, either maintaining habitual lifestyle habits or in combination with energy restriction and/or increased physical activity for an average of 12 weeks.
Specific strains belonging to the genus Lactobacillus and Bifidobacterium were the most used and those that showed the best results in reducing body weight.
Both probiotics and synbiotics have the potential to help in weight loss in overweight and obese populations.❞
This slightly older (2015) systematic review and meta-analysis found the opposite:
❝Collectively, the RCTs examined in this meta-analysis indicated that probiotics have limited efficacy in terms of decreasing body weight and BMI and were not effective for weight loss.❞
Source: Probiotics for weight loss: a systematic review and meta-analysis
And in case that’s not balanced enough, this 2020 randomized controlled trial got mixed results:
❝Regression analysis performed to correlate abundance of species following supplementation with body composition parameters and biomarkers of obesity found an association between a decrease over time in blood glucose and an increase in Lactobacillus abundance, particularly in the synbiotic group.
However, the decrease over time in body mass, BMI, waist circumstance, and body fat mass was associated with a decrease in Bifidobacterium abundance.❞
Source: Effects of Synbiotic Supplement on Human Gut Microbiota, Body Composition and Weight Loss in Obesity
Summary
Probiotics may or may not work for weight loss.
In all likelihood, it depends on the blend of cultures contained in the supplement. It’s possible that Lactobacillus is more beneficial for weight loss than Bifidobacterium, which latter may actually reduce weight loss.
Or it might not, because that was just one study and correlation ≠ causation!
We’d love to give you a hard-and-fast answer, but if the data doesn’t support a hard-and-fast answer, we’re not going to lie to you.
What we can say for sure though is that probiotics come with very many health benefits, so whether or not weight loss is one of them, they’re a good thing to have for most people.
Some further articles that may interest you:
- How Much Difference Do Probiotic Supplements Make, Really? ← the aforementioned article
- Making Friends With Your Gut (You Can Thank Us Later) ← gut health 101
- Burn! How To Boost Your Metabolism ← these things can help change your metabolic base rate, which is highly relevant to weight loss
- How To Do HIIT (Without Wrecking Your Body) ←unlike most forms of exercise, which cause the body to slow the metabolism afterwards to compensate, high-intensity interval training results in an increased metabolic rate (so generally: fat-burning) for several hours after training.
Take care!
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Caramelized Caraway Cabbage
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Cabbage is an underrated vegetable for its many nutrients and its culinary potential—here’s a great way to make it a delectable starter or respectable side.
You will need
- 1 medium white cabbage, sliced into 1″ thick slabs
- 1 tbsp extra-virgin olive oil
- 1 tbsp caraway seeds
- 1 tsp black pepper
- ½ tsp turmeric
- ¼ tsp MSG or ½ tsp low-sodium salt
Method
(we suggest you read everything at least once before doing anything)
1) Preheat the oven to 400℉ / 200℃.
2) Combine the non-cabbage ingredients in a small bowl, whisking to mix thoroughly—with a tiny whisk if you have one, but a fork will work if necessary.
3) Arrange the cabbage slices on a lined baking tray and brush the seasoning-and-oil mixture over both sides of each slice.
4) Roast for 20–25 minutes until the cabbage is tender and beginning to caramelize.
5) Serve warm.
Enjoy!
Want to learn more?
For those interested in some of the science of what we have going on today:
- Curcumin (Turmeric) is worth its weight in gold
- Black Pepper’s Impressive Anti-Cancer Arsenal (And More)
- Avocado Oil vs Olive Oil – Which is Healthier?
Take care!
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Calculate (And Enjoy) The Perfect Night’s Sleep
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This is Dr. Michael Breus, a clinical psychologist and sleep specialist, and he wants you to get a good night’s sleep, every night.
First, let’s assume you know a lot of good advice about how to do that already in terms of environment and preparation, etc. If you want a recap before proceeding, then we recommend:
Get Better Sleep: Beyond The Basics
Now, what does he want to add?
Wake up refreshed
Of course, how obtainable this is will depend on the previous night’s sleep, but there is something important we can do here regardless, and it’s: beat sleep inertia.
Sleep inertia is what happens when we wake up groggy (for reasons other than being ill, drugged, etc) rather than refreshed. It’s not actually related to how much sleep we have, though!
Rather, it pertains to whether we woke up during a sleep cycle, or between cycles:
- If we wake up between sleep cycles, we’ll avoid sleep inertia.
- If we wake up during a sleep cycle, we’ll be groggy.
Deep sleep generally occurs in 90-minute blocks, albeit secretly that is generally 3× 20 minute blocks in a trenchcoat, with transition periods between, during which the brainwaves change frequency.
REM sleep generally occurs in 20 minute blocks, and will usually arrive in series towards the end of our natural sleep period, to fit neatly into the last 90-minute cycle.
Sometimes these will appear a little out of order, because we are complicated organic beings, but those are the general trends.
In any case, the take-away here is: interrupt them at your peril. You need to wake up between cycles. There are two ways you can do this:
- Carefully calculate everything, and set a very precise alarm clock (this will work so long as you are correct in guessing how long it will take you to fall asleep)
- Use a “sunrise” lamp alarm clock, that in the hour approaching your set alarm time, will gradually increase the light. Because the body will not naturally wake up during a cycle unless a threat is perceived (loud noise, physical rousing, etc), the sunrise lamp method means that you will wake up between sleep cycles at some point during that hour (towards the beginning or end, depending on what your sleep balance/debt is like).
Do not sleep in (even if you have a sleep debt); it will throw everything out.
Caffeine will not help much in the morning
Assuming you got a reasonable night’s sleep, your brain has been cleansed of adenosine (a sleepy chemical), and if you are suffering from sleep inertia, the grogginess is due to melatonin (a different sleepy chemical).
Caffeine is an adenosine receptor blocker, so that will do nothing to mitigate the effects of melatonin in your brain that doesn’t have any meaningful quantity of adenosine in it in the morning.
Adenosine gradually accumulates in the brain over the course of the day (and then gets washed out while we sleep), so if you’re sleepy in the afternoon (for reasons other than: you just had a nap and now have sleep inertia again), then caffeine can block that adenosine in the afternoon.
Of course, caffeine is also a stimulant (it increases adrenaline levels and promotes vasoconstriction), but its effects at healthily small doses are modest for most people, and you’d do better by splashing cold water on your face and/or listening to some upbeat music.
Learn more: The Two Sides Of Caffeine
Time your naps correctly (if you take naps)
Dr. Breus has a lot to say about this, based on a lot of clinical research, but as it’s entirely consistent with what we’ve written before (based on the exact same research), to save space we’ll link to that here:
How To Be An Expert Nap-Artist (With No “Sleep-Hangovers”)
Calculate your bedtime correctly
Remember what we said about sleep cycles? This means that that famous “7–9 hours sleep” is actually “either 7½ or 9 hours sleep”—because those are multiples of 90 minutes, whereas 8 hours (for example) is not.
So, consider the time you want to get up (ideally, this should be relatively early, and the same time every day), and then count backwards either 7½ or 9 hours sleep (you choose), add 20–30 minutes to fall asleep, and that’s your bedtime.
So for example: if you want to have 7½ hours sleep and get up at 6am, then your bedtime is anywhere between 10pm and 10:10pm.
Remember how we said not to sleep in, even if you have a sleep debt? Now is the time to pay it off, if you have one. If you normally sleep 7½ hours, then make tonight a 9-hour sleep (plus 20–30 minutes to fall asleep). This means you’ll still get up at 6am, but your bedtime is now anywhere between 8:30pm and 8:40pm.
Want to know more from Dr. Breus?
You might like this excellent book of his that we reviewed a while back:
The Power of When – by Dr. Michael Breus
Enjoy!
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What Teas To Drink Before Bed (By Science!)
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Which Sleepy Tea?
Herbal “tea” preparations (henceforth we will write it without the quotation marks, although these are not true teas) are popular for winding down at the end of a long day ready for a relaxing sleep.
Today we’ll look at the science for them! We’ll be brief for each, because we’ve selected five and have only so much room, but here goes:
Camomile
Simply put, it works and has plenty of good science for it. Here’s just one example:
❝Noteworthy, our meta-analysis showed a significant improvement in sleep quality after chamomile administration❞
Also this writer’s favourite relaxation drink!
(example on Amazon if you want some)
Lavender
We didn’t find robust science for its popularly-claimed sedative properties, but it does appear to be anxiolytic, and anxiety gets in the way of sleep, so while lavender may not be a sedative, it may calm a racing mind all the same, thus facilitating better sleep:
(example on Amazon if you want some)
Magnolia
Animal study for the mechanism:
Human study for “it is observed to help humans sleep better”:
As you can see from the title, its sedative properties weren’t the point of the study, but if you click through to read it, you can see that they found (and recorded) this benefit anyway
(example on Amazon if you want some)
Passionflower
There’s not a lot of evidence for this one, but there is some. Here’s a small study (n=41) that found:
❝Of six sleep-diary measures analysed, sleep quality showed a significantly better rating for passionflower compared with placebo (t(40) = 2.70, p < 0.01). These initial findings suggest that the consumption of a low dose of Passiflora incarnata, in the form of tea, yields short-term subjective sleep benefits for healthy adults with mild fluctuations in sleep quality.❞
So, that’s not exactly a huge body of evidence, but it is promising.
(example on Amazon if you want some)
Valerian
We’ll be honest, the science for this one is sloppy. It’s very rare to find Valerian tested by itself (or sold by itself; we had to dig a bit to find one for the Amazon link below), and that skews the results of science and renders any conclusions questionable.
And the studies that were done? Dubious methods, and inconclusive results:
Nevertheless, if you want to try it for yourself, you can do a case study (i.e., n=1 sample) if not a randomized controlled trial, and let us know how it goes 🙂
(example on Amazon if you want some)
Summary
- Valerian we really don’t have the science to say anything about it
- Passionflower has some nascent science for it, but not much
- Lavender is probably not soporific, but it is anxiolytic
- Magnolia almost certainly helps, but isn’t nearly so well-backed as…
- Camomile comes out on top, easily—by both sheer weight of evidence, and by clear conclusive uncontroversial results.
Enjoy!
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The Complete Anti-Inflammatory Diet for Beginners – by Dorothy Calimeris and Lulu Cook
10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.
First, about the authors: notwithstanding the names, Calimeris is the cook, and Cook is the nutritionist (and an RDN at that).
As for the book: we get a good primer on the science of inflammation, what it is, why it happens, what things are known to cause/trigger it, and what things are known to fight it. They do also go outside of nutrition a bit for this, speaking briefly on other lifestyle factors too, but the main focus is of course nutrition.
As for the recipes: while distinctly plants-forward (as one might expect of an anti-inflammatory eating book), it’s not outright vegan or even vegetarian, indeed, in the category of main dishes, there are sections for:
- Vegetarian and vegan
- Fish and shellfish
- Poultry and meat
…as well as, before and after those, sections for breakfast and brunch and snacks and sweets. As well as a not-to-be-underestimated section, for sauces, condiments, and dressings. This is important, because those are quite often the most inflammatory parts of an otherwise healthy meal! So being able to make anti-inflammatory versions is a real boon.
The recipes are mostly not illustrated, but the steps are very clearly described and easy to follow.
Bottom line: if inflammation is currently on your to-tackle list, this book will be an excellent companion in the kitchen.
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Proteins Of The Week
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This week’s news round-up is, entirely by chance, somewhat protein-centric in one form or another. So, check out the bad, the very bad, the mostly good, the inconvenient, and the worst:
Mediterranean diet vs the menopause
Researchers looked at hundreds of women with an average age of 51, and took note of their dietary habits vs their menopause symptoms. Most of them were consuming soft drinks and red meat, and not good in terms of meeting the recommendations for key food groups including vegetables, legumes, fruit, fish and nuts, and there was an association between greater adherence to Mediterranean diet principles, and better health.
Read in full: Fewer soft drinks and less red meat may ease menopause symptoms: Study
Related: Four Ways To Upgrade The Mediterranean Diet
Listeria in meat
This one’s not a study, but it is relevant important news. The headline pretty much says it all, so if you don’t eat meat, this isn’t one you need to worry about any further than that. If you do eat meat, though, you might want to check out the below article to find out whether the meat you eat might be carrying listeria:
Read in full: Almost 10 million pounds of meat recalled due to Listeria danger
Related: Frozen/Thawed/Refrozen Meat: How Much Is Safety, And How Much Is Taste?
Brawn and brain?
A study looked at cognitively healthy older adults (of whom, 57% women), and found an association between their muscle strength and their psychological wellbeing. Note that when we said “cognitively healthy”, this means being free from dementia etc—not necessarily psychologically health in all respects, such as also being free from depression and enjoying good self-esteem.
Read in full: Study links muscle strength and mental health in older adults
Related: Staying Strong: Tips To Prevent Muscle Loss With Age
The protein that blocks bone formation
This one’s more clinical but definitely of interest to any with osteoporosis or at high risk of osteoporosis. Researchers identified a specific protein that blocks osteoblast function, thus more of this protein means less bone production. Currently, this is not something that we as individuals can do anything about at home, but it is promising for future osteoporosis meds development.
Read in full: Protein blocking bone development could hold clues for future osteoporosis treatment
Related: Which Osteoporosis Medication, If Any, Is Right For You?
Rabies risk
People associate rabies with “rabid dogs”, but the biggest rabies threat is actually bats, and they don’t even need to necessarily bite you to confer the disease (it suffices to have licked the skin, for instance—and bats are basically sky-puppies who will lick anything). Because rabies has a 100% fatality rate in unvaccinated humans, this is very serious. This means that if you wake up and there’s a bat in the house, it doesn’t matter if it hasn’t bitten anyone; get thee to a hospital (where you can get the vaccine before the disease takes hold; this will still be very unpleasant but you’ll probably survive so long as you get the vaccine in time).
Read in full: What to know about bats and rabies
Related: Dodging Dengue In The US ← much less serious than rabies, but still not to be trifled with—particularly noteworthy if you’re in an area currently affected by floodwaters or even just unusually heavy rain, by the way, as this will leave standing water in which mosquitos breed.
Take care!
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Driving under the influence of marijuana: An explainer and research roundup
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Update 1: On May 16, 2024, the U.S. Department of Justice sent a proposed rule to the Federal Register to downgrade marijuana from a Schedule I to a Schedule III drug. This is the first step in a lengthy approval process that starts with a 60-day comment period.
Update 2: Two recent research studies were added to the “Studies on marijuana and driving” section of this piece on July 18, 2024.
As marijuana use continues to rise and state-level marijuana legalization sweeps the U.S., researchers and policymakers are grappling with a growing public safety concern: marijuana-impaired driving.
As of April 2023, 38 U.S. states had legalized medical marijuana and 23 had legalized its recreational use, according to the National Conference of State Legislatures. Recreational or medical marijuana measures are on the ballot in seven states this year.
The issue of marijuana-impaired driving has not been an easy one to tackle because, unlike alcohol, which has well-established thresholds of impairment, the metrics for marijuana’s effects on driving remain rather elusive.
“We don’t have that kind of deep knowledge right now and it’s not because of lack of trying,” says Dr. Guohua Li, professor of epidemiology and the founding director of the Center for Injury Science and Prevention at Columbia University.
“Marijuana is very different from alcohol in important ways,” says Li, who has published several studies on marijuana and driving. “And one of them is that the effect of marijuana on cognitive functions and behaviors is much more unpredictable than alcohol. In general, alcohol is a depressant drug. But marijuana could act on the central nervous system as a depressant, a stimulant, and a hallucinogenic substance.”
Efforts to create a breathalyzer to measure the level of THC, the main psychoactive compound found in the marijuana plant, have largely failed, because “the THC molecule is much bigger than ethanol and its behavior after ingestion is very different from alcohol,” Li says.
Currently, the two most common methods used to measure THC concentration to identify impaired drivers are blood and saliva tests, although there’s ongoing debate about their reliability.
Marijuana, a term interchangeably used with cannabis, is the most commonly used federally illegal drug in the U.S.: 48.2 million people, or about 18% of Americans reported using it at least once in 2019, according to the latest available data from the Centers for Disease Control and Prevention. Worldwide, 2.5% of the population consumes marijuana, according to the World Health Organization.
Marijuana is legal in several countries, including Canada, where it was legalized in 2018. Despite state laws legalizing cannabis, it remains illegal at the federal level in the U.S.
As states grapple with the contentious issue of marijuana legalization, the debate is not just about public health, potential tax revenues and economic interests. At the heart of the discussion is also the U.S. criminal justice system.
Marijuana is shown to have medicinal qualities and, compared with substances like alcohol, tobacco, and opioids, it has relatively milder health risks. However, it’s not risk-free, a large body of research has shown.
Marijuana consumption can lead to immediate effects such as impaired muscle coordination and paranoia, as well as longer-term effects on mental health and cognitive functions — and addiction. As its use becomes more widespread, researchers are trying to better understand the potential hazards of marijuana, particularly for younger users whose brains are in critical stages of development.
Marijuana and driving
The use of marijuana among drivers, passengers and pedestrians has increased steadily over the past two decades, Li says.
Compared with the year 2000, the proportion of U.S. drivers on the road who are under the influence of marijuana has increased by several folds, between five to 10 times, based on toxicology testing of people who died in car crashes, Li says.
A 2022 report from the National Transportation Safety Board finds alcohol and cannabis are the two most commonly detected drugs among drivers arrested for impaired driving and fatally injured drivers. Most drivers who tested positive for cannabis also tested positive for another potentially impairing drug.
“Although cannabis and many other drugs have been shown to impair driving performance and are associated with increased crash risk, there is evidence that, relative to alcohol, awareness about the potential dangers of driving after using other drugs is lower,” according to the report.
Indeed, many U.S. adults perceive daily marijuana use or exposure to its smoke safer than tobacco, even though research finds otherwise.
Several studies have demonstrated marijuana’s impact on driving.
Marijuana use can reduce the drivers’ ability to pay attention, particularly when they are performing multiple tasks, research finds. It also slows reaction time and can impair coordination.
“The combination is that you potentially have people who are noticing hazards later, braking slower and potentially not even noticing hazards because of their inability to focus on competing things on the road,” says Dr. Daniel Myran, an assistant professor at the Department of Family Medicine and health services researcher at the University of Ottawa.
In a study published in September in JAMA Network Open, Myran and colleagues find that from 2010 to 2021 the rate of cannabis-involved traffic injuries that led to emergency department visits in Ontario, Canada, increased by 475%, from 0.18 per 1,000 traffic injury emergency department visits in 2010 to 1.01 visits in 2021.
To be sure, cannabis-involved traffic injuries made up a small fraction of all traffic injury-related visits to hospital emergency departments. Out of 947,604 traffic injury emergency department visits, 426 had documented cannabis involvement.
Myran cautions the increase shouldn’t be solely attributed to marijuana legalization. It captures changing societal attitudes toward marijuana and acceptance of cannabis use over time in the lead-up to legalization. In addition, it may reflect an increasing awareness among health care providers about cannabis-impaired driving, and they may be more likely to ask about cannabis use and document it in medical charts, he says.
“When you look at the 475% increase in cannabis involvement in traffic injuries, rather than saying legalizing cannabis has caused the roads to be unsafe and is a public health disaster, it’s that cannabis use appears to be growing as a risk for road traffic injuries and that there seem to be more cannabis impaired drivers on the road,” Myran says. “Legalization may have accelerated this trend. Faced with this increase, we need to think about what are public health measures and different policy interventions to reduce harms from cannabis-impaired driving.”
Setting a legal limit for marijuana-impaired driving
Setting a legal limit for marijuana-impaired driving has not been easy. Countries like Canada and some U.S. states have agreed upon a certain level of THC in blood, usually between 1 to 5 nanograms per milliliter. Still, some studies have found those limits to be weak indicators of cannabis-impaired driving.
When Canada legalized recreational marijuana in 2018, it also passed a law that made it illegal to drive with blood THC levels of more than 2 nanograms. The penalties are more severe for blood THC levels above 5 nanograms. The blood test is done at the police station for people who are pulled over and are deemed to be drug impaired.
In the U.S., five states — Ohio, Illinois, Montana, Washington and Nevada — have “per se laws,” which set a specific amount of THC in the driver’s blood as evidence of impaired driving, according to the National Conference of State Legislatures. That limit ranges between 2 and 5 nanograms of THC per milliliter of blood.
Colorado, meanwhile, has a “permissible inference law,” which states that it’s permissible to assume the driver was under the influence if their blood THC level is 5 nanograms per milliliter or higher, according to NCSL.
Twelve states, most which have legalized some form of marijuana of use, have zero tolerance laws for any amount of certain drugs, including THC, in the body.
The remaining states have “driving under the influence of drugs” laws. Among those states, Alabama and Michigan, have oral fluid roadside testing program to screen drivers for marijuana and other drugs, according to NCSL.
In May this year, the U.S. Department of Transportation published a final rule that allows employers to use saliva testing for commercially licensed drivers, including truck drivers. The rule, which went into effect in June, sets the THC limit in saliva at 4 nanograms.
Saliva tests can detect THC for 8 to 24 hours after use, but the tests are not perfect and can results in false positives, leading some scientists to argue against using them in randomly-selected drivers.
In a 2021 report, the U.S. National Institute of Justice, the research and development arm of the Department of Justice, concluded that THC levels in bodily fluids, including blood and saliva “were not reliable indicators of marijuana intoxication.”
Studies on marijuana and driving
Over the past two decades, many studies have shown marijuana use can impair driving. However, discussions about what’s the best way to measure the level of THC in blood or saliva are ongoing. Below, we highlight and summarize several recent studies that address the issue. The studies are listed in order of publication date. We also include a list of related studies and resources to inform your audiences.
State Driving Under the Influence of Drugs Laws
Alexandra N. Origenes, Sarah A. White, Emma E. McGinty and Jon S. Vernick. Journal of Law, Medicine & Ethics, July 2024.Summary: As of January 2023, 33 states and D.C. had a driving under the influence of drugs law for at least one drug other than cannabis. Of those, 29 states and D.C. had a law specifically for driving under the influence of cannabis, in addition to a law for driving under the influence of other drugs. Four states had a driving under the influence of drug laws, excluding cannabis. Meanwhile, 17 states had no law for driving under the influence of drugs, including cannabis. “The 17 states lacking a DUID law that names specific drugs should consider enacting such a law. These states already have expressed their concern — through legislation — with drug-impaired driving. However, failure to name specific drugs is likely to make the laws more difficult to enforce. These laws may force courts and/or law enforcement to rely on potentially subjective indicators of impairment,” the authors write.
Associations between Adolescent Marijuana Use, Driving After Marijuana Use and Recreational Retail Sale in Colorado, USA
Lucas M. Neuroth, et al. Substance Use & Misuse, October 2023.Summary: Researchers use data from four waves (2013, 2015, 2017 and 2019) of the Healthy Kids Colorado Survey, including 47,518 students 15 and older who indicated that they drove. They find 20.3% of students said that they had used marijuana in the past month and 10.5% said they had driven under the influence of marijuana. They find that the availability of recreational marijuana in stores was associated with an increased prevalence of using marijuana one to two times in the past month and driving under the influence of marijuana at least once. “Over the study period, one in ten high school age drivers engaged in [driving after marijuana use], which is concerning given the high risk of motor vehicle-related injury and death arising from impaired driving among adolescents,” the authors write.
Are Blood and Oral Fluid Δ9-tetrahydrocannabinol (THC) and Metabolite Concentrations Related to Impairment? A Meta-Regression Analysis
Danielle McCartney, et al. Neuroscience & Biobehavioral Reviews, March 2022.Summary: Commonly used THC measurements may not be strong indicators of driving impairment. While there is a relationship between certain biomarkers like blood THC concentrations and impaired driving, this correlation is often weak. The study underscores the need for more nuanced and comprehensive research on this topic, especially as cannabis usage becomes more widespread and legally accepted.
The Effects of Cannabis and Alcohol on Driving Performance and Driver Behaviour: A Systematic Review and Meta-Analysis
Sarah M. Simmons, Jeff K. Caird, Frances Sterzer and Mark Asbridge. Addiction, January 2022.Summary: This meta-analysis of experimental driving studies, including driving simulations, confirms that cannabis impairs driving performance, contrary to some beliefs that it might enhance driving abilities. Cannabis affects lateral control and speed — typically increasing lane excursions while reducing speed. The combination of alcohol and marijuana appears worse than either alone, challenging the idea that they cancel each other out.
Cannabis Legalization and Detection of Tetrahydrocannabinol in Injured Drivers
Jeffrey R. Brubacher, et al. The New England Journal of Medicine, January 2022.Summary: Following the legalization of recreational marijuana in Canada, there was a notable increase in injured drivers testing positive for THC, especially among those 50 years of age or older. This rise in cannabis-related driving incidents occurred even with new traffic laws aiming to deter cannabis-impaired driving. This uptick began before legalization became official, possibly due to perceptions that cannabis use was soon-to-be legal or illegal but not enforced. The data suggests that while legalization has broad societal impacts, more comprehensive strategies are needed to deter driving under the influence of cannabis and raise public awareness about its risks.
Cannabis and Driving
Godfrey D. Pearlson, Michael C. Stevens and Deepak Cyril D’Souza. Frontiers in Psychiatry, September 2021.Summary: Cannabis-impaired driving is a growing public health concern, and studies show that such drivers are more likely to be involved in car crashes, according to this review paper. Drivers are less affected by cannabis than they are by alcohol or cocaine, but the problem is expected to escalate with increasing cannabis legalization and use. Unlike alcohol, THC’s properties make it challenging to determine direct impairment levels from testing results. Current roadside tests lack precision in detecting genuine cannabis-impaired drivers, leading to potential wrongful convictions. Moreover, there is a pressing need for research on the combined effects of alcohol and cannabis on driving, as well as the impact of emerging popular forms of cannabis, like concentrates and edibles. The authors recommend public awareness campaigns about the dangers of driving under the influence of cannabis, similar to those against drunk driving, to address misconceptions. Policymakers should prioritize science-based decisions and encourage further research in this domain.
Demographic And Policy-Based Differences in Behaviors And Attitudes Towards Driving After Marijuana Use: An Analysis of the 2013–2017 Traffic Safety Culture Index
Marco H. Benedetti, et al. BMC Research Notes, June 2021.Summary: The study, based on a U.S. survey, finds younger, low-income, low-education and male participants were more tolerant of driving after marijuana consumption. Notably, those in states that legalized medical marijuana reported driving after use more frequently, aligning with studies indicating a higher prevalence of THC detection in drivers from these states. Overall, while the majority perceive driving after marijuana use as dangerous, not all research agrees on its impairment effects. Existing studies highlight that marijuana impacts motor skills and executive functions, yet its direct correlation with crash risk remains debated, given the variations in individual tolerance and how long THC remains in the system.
Driving Under the Influence of Cannabis: A Framework for Future Policy
Robert M. Chow, et al.Anesthesia & Analgesia, June 2019.Summary: The study presents a conceptual framework focusing on four main domains: legalization, driving under the influence of cannabis, driver impairment, and motor vehicle accidents. With the growing legalization of cannabis, there’s an anticipated rise in cannabis-impaired driving cases. The authors group marijuana users into infrequent users who show significant impairment with increased THC blood levels, chronic users with minimal impairment despite high THC levels, and those with consistent psychomotor deficits. Current challenges lie in the lack of standardized regulation for drivers influenced by cannabis, primarily because of state-to-state variability and the absence of a federal statutory limit for blood THC levels. European nations, however, have established thresholds for blood THC levels, ranging from 0.5 to 50.0 micrograms per liter depending on whether blood or blood serum are tested. The authors suggest the combined use of alcohol and THC blood tests with a psychomotor evaluation by a trained professional to determine impairment levels. The paper stresses the importance of creating a structured policy framework, given the rising acceptance and use of marijuana in society.
Additional research
Cannabis-Involved Traffic Injury Emergency Department Visits After Cannabis Legalization and Commercialization
Daniel T. Myran, et al. JAMA Network Open, September 2023.Driving Performance and Cannabis Users’ Perception of Safety: A Randomized Clinical Trial
Thomas D. Marcotte, et al. JAMA Psychiatry, January 2022.Medicinal Cannabis and Driving: The Intersection of Health and Road Safety Policy
Daniel Perkins, et al. International Journal of Drug Policy, November 2021.Prevalence of Marijuana Use Among Trauma Patients Before and After Legalization of Medical Marijuana: The Arizona Experience
Michael Levine, et al. Substance Abuse, July 2021.Self-Reported Driving After Marijuana Use in Association With Medical And Recreational Marijuana Policies
Marco H. Benedetti, et al. International Journal of Drug Policy, June 2021.Cannabis and Driving Ability
Eric L. Sevigny. Current Opinion in Psychology, April 2021.The Failings of per se Limits to Detect Cannabis-Induced Driving Impairment: Results from a Simulated Driving Study
Thomas R. Arkell, et al. Traffic Injury Prevention, February 2021.Risky Driving Behaviors of Drivers Who Use Alcohol and Cannabis
Tara Kelley-Baker, et al. Transportation Research Record, January 2021.Direct and Indirect Effects of Marijuana Use on the Risk of Fatal 2-Vehicle Crash Initiation
Stanford Chihuri and Guohua Li. Injury Epidemiology, September 2020Cannabis-Impaired Driving: Evidence and the Role of Toxicology Testing
Edward C. Wood and Robert L. Dupont. Cannabis in Medicine, July 2020.Association of Recreational Cannabis Laws in Colorado and Washington State With Changes in Traffic Fatalities, 2005-2017
Julian Santaella-Tenorio, et al. JAMA Internal Medicine, June 2020.Marijuana Decriminalization, Medical Marijuana Laws, and Fatal Traffic Crashes in US Cities, 2010–2017
Amanda Cook, Gregory Leung and Rhet A. Smith. American Journal of Public Health, February 2020.Cannabis Use in Older Drivers in Colorado: The LongROAD Study
Carolyn G. DiGuiseppi, et al. Accident Analysis & Prevention, November 2019.Crash Fatality Rates After Recreational Marijuana Legalization in Washington and Colorado
Jayson D. Aydelotte, et al. American Journal of Public Health, August 2017.Marijuana-Impaired Driving: A Report to Congress
National Highway Traffic Safety Administration, July 2017Interaction of Marijuana And Alcohol on Fatal Motor Vehicle Crash Risk: A Case–Control Study
Stanford Chihuri, Guohua Li and Qixuan Chen. Injury Epidemiology, March 2017.US Traffic Fatalities, 1985–2014, and Their Relationship to Medical Marijuana Laws
Julian Santaella-Tenorio, et al. American Journal of Public Health, February 2017.Delays in DUI Blood Testing: Impact on Cannabis DUI Assessments
Ed Wood, Ashley Brooks-Russell and Phillip Drum. Traffic Injury Prevention, June 2015.Establishing Legal Limits for Driving Under the Influence of Marijuana
Kristin Wong, Joanne E. Brady and Guohua Li. Injury Epidemiology, October 2014.Cannabis Effects on Driving Skills
Rebecca L. Hartman and Marilyn A. Huestis. Clinical Chemistry, March 2014.Acute Cannabis Consumption And Motor Vehicle Collision Risk: Systematic Review of Observational Studies and Meta-Analysis
Mark Asbridge, Jill A. Hayden and Jennifer L. Cartwright. The BMJ, February 2012.Resources for your audiences
The following resources include explainers from federal agencies and national organizations. You’re free to use images and graphics from federal agencies.
- CDC’s main marijuana page.
- CDC’s marijuana data and statistics.
- Marijuana Drug Facts from the National Institute on Drug Abuse.
- Health Effects of Marijuana from the CDC.
- Learn About Marijuana Risks from the Substance Abuse and Mental Health Services Administration.
- Marijuana and Lung Health from the American Lung Association.
- Substance Use Disorder 101 from the U.S. Department of Health & Human Services.
- What You Need To Know About Marijuana Use and Driving from the CDC.
- Does marijuana use affect driving? from the National Institute on Drug Abuse.
- Drug-Impaired Driving from the National Highway Traffic Safety Administration.
This article first appeared on The Journalist’s Resource and is republished here under a Creative Commons license.
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