Creatine’s Brain Benefits Increase With Age

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Creatine is generally thought of as a body-building supplement, and for most young people, that’s all it is. But with extra years come extra advantages, and creatine starts to confer cognitive benefits. Dr. Brad Stanfield shares the science:

What the science says

Although 95% of creatine is stored in muscles, 5% is found in the brain, where it helps produce energy needed for brain processes (and that’s a lot of energy—about 20% of our body’s metabolic base rate is accounted for by our brain).

In this video, Dr. Stanfield shares studies showing creatine improving memory, especially in older adults—and also in vegetarians/vegans, since creatine is found in meat (just like in our own bodies, which are also made of meat) and not in plants. On the meta-analysis level, a systematic review concluded that creatine supplementation indeed improves memory, with stronger effects observed in older adults.

Dr. Stanfield also addresses the safety concerns about creatine, which, on balance, are not actually supported by the science (of course, always consult your own doctor to be sure, as your case could vary).

As for dosage, 5g/day is recommended. For more on all of this plus links to the studies cited, enjoy:

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Want to learn more?

You might also like to read:

Creatine: Very Different For Young & Old People

Take care!

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  • How To Make Drinking Less Harmful

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    Making Drinking Less Harmful

    We often talk of the many ways alcohol harms our health, and we advocate for reducing (or eliminating) its consumption. However, it’s not necessarily as easy as all that, and it might not even be a goal that everyone has. So, if you’re going to imbibe, what can you do to mitigate the harmful effects of alcohol?

    There is no magical solution

    Sadly. If you drink alcohol, there will be some harmful effects, and nothing will completely undo that. But there are some things that can at least help—read on to learn more!

    Coffee

    It’s not the magical sober-upperer that some would like it to be, but it is good against the symptoms of alcohol intoxication, and slightly reduces the harm to your body, because it is:

    • Hydrating (whereas alcohol is dehydrating)
    • A source of antioxidants (whereas alcohol causes oxidative stress, which has nothing to do with psychological stress, and is a kind of cellular damage)
    • A stimulant, assuming it is not decaffeinated (it’s worth noting that its stimulant effects work partly by triggering vasoconstriction, which is the opposite of the vasodilation caused by alcohol)

    To this end, the best coffee for anti-alcohol effects should be:

    • Caffeinated, and strong
    • Long (we love espresso, but we need hydration here and that comes from volume!)
    • Without sugar (you don’t want to create an adverse osmotic gradient to leech water from your body)

    As for milk/cream/whatever, have it or don’t, per your usual preference. It won’t make any difference to the alcohol in your system.

    Antioxidants, polyphenols, flavonoids, and things with similar mechanisms

    We mentioned that coffee contains antioxidants, but if you want to really bring out the heavy guns, taking more powerful antioxidants can help a lot. If you don’t have the luxury of enjoying berries and cacao nibs by the handful, supplements that have some similar benefits are a perfectly respectable choice.

    For example, you might want to consider green tea extract:

    L-theanine 200mg (available on Amazon)

    Specialist anti-alcohol drugs

    These are somewhat new and the research is still ongoing, but for example:

    Dihydromyricetin (DHM) as a novel anti-alcohol intoxication medication

    In short, DHM is a flavonoid (protects against the oxidative stress caused by alcohol, and has been found to reduce liver damage—see the above link) and also works on GABA-receptors (reduces alcohol withdrawal symptoms after cessation of drinking, and thus also reduces hangovers).

    Once again: the marketing claims of such drugs may be bold, but there’s a lot that’s not known and they’re not a magic pill. They do NOT mean you can take them alongside drinking and drink what you like with impunity. However, they may help mitigate some of the harmful effects of alcohol. If you wish to try them, these can be purchased at pharmacies or online, for example:

    Alcohol Defense Capsules (available on Amazon)

    Bottom line

    Alcohol is bad for your health and none of the above will eliminate the health risks. But, if you’re going to have alcohol, then having the above things as well may at least somewhat reduce the harm done.

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  • What will aged care look like for the next generation? More of the same but higher out-of-pocket costs

    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.

    Aged care financing is a vexed problem for the Australian government. It is already underfunded for the quality the community expects, and costs will increase dramatically. There are also significant concerns about the complexity of the system.

    In 2021–22 the federal government spent A$25 billion on aged services for around 1.2 million people aged 65 and over. Around 60% went to residential care (190,000 people) and one-third to home care (one million people).

    The final report from the government’s Aged Care Taskforce, which has been reviewing funding options, estimates the number of people who will need services is likely to grow to more than two million over the next 20 years. Costs are therefore likely to more than double.

    The taskforce has considered what aged care services are reasonable and necessary and made recommendations to the government about how they can be paid for. This includes getting aged care users to pay for more of their care.

    But rather than recommending an alternative financing arrangement that will safeguard Australians’ aged care services into the future, the taskforce largely recommends tidying up existing arrangements and keeping the status quo.

    No Medicare-style levy

    The taskforce rejected the aged care royal commission’s recommendation to introduce a levy to meet aged care cost increases. A 1% levy, similar to the Medicare levy, could have raised around $8 billion a year.

    The taskforce failed to consider the mix of taxation, personal contributions and social insurance which are commonly used to fund aged care systems internationally. The Japanese system, for example, is financed by long-term insurance paid by those aged 40 and over, plus general taxation and a small copayment.

    Instead, the taskforce puts forward a simple, pragmatic argument that older people are becoming wealthier through superannuation, there is a cost of living crisis for younger people and therefore older people should be required to pay more of their aged care costs.

    Separating care from other services

    In deciding what older people should pay more for, the taskforce divided services into care, everyday living and accommodation.

    The taskforce thought the most important services were clinical services (including nursing and allied health) and these should be the main responsibility of government funding. Personal care, including showering and dressing were seen as a middle tier that is likely to attract some co-payment, despite these services often being necessary to maintain independence.

    The task force recommended the costs for everyday living (such as food and utilities) and accommodation expenses (such as rent) should increasingly be a personal responsibility.

    Aged care resident eats dinner from a tray
    Aged care users will pay more of their share for cooking and cleaning.
    Lizelle Lotter/Shutterstock

    Making the system fairer

    The taskforce thought it was unfair people in residential care were making substantial contributions for their everyday living expenses (about 25%) and those receiving home care weren’t (about 5%). This is, in part, because home care has always had a muddled set of rules about user co-payments.

    But the taskforce provided no analysis of accommodation costs (such as utilities and maintenance) people meet at home compared with residential care.

    To address the inefficiencies of upfront daily fees for packages, the taskforce recommends means testing co-payments for home care packages and basing them on the actual level of service users receive for everyday support (for food, cleaning, and so on) and to a lesser extent for support to maintain independence.

    It is unclear whether clinical and personal care costs and user contributions will be treated the same for residential and home care.

    Making residential aged care sustainable

    The taskforce was concerned residential care operators were losing $4 per resident day on “hotel” (accommodation services) and everyday living costs.

    The taskforce recommends means tested user contributions for room services and everyday living costs be increased.

    It also recommends that wealthier older people be given more choice by allowing them to pay more (per resident day) for better amenities. This would allow providers to fully meet the cost of these services.

    Effectively, this means daily living charges for residents are too low and inflexible and that fees would go up, although the taskforce was clear that low-income residents should be protected.

    Moving from buying to renting rooms

    Currently older people who need residential care have a choice of making a refundable up-front payment for their room or to pay rent to offset the loans providers take out to build facilities. Providers raise capital to build aged care facilities through equity or loan financing.

    However, the taskforce did not consider the overall efficiency of the private capital market for financing aged care or alternative solutions.

    Instead, it recommended capital contributions be streamlined and simplified by phasing out up-front payments and focusing on rental contributions. This echoes the royal commission, which found rent to be a more efficient and less risky method of financing capital for aged care in private capital markets.

    It’s likely that in a decade or so, once the new home care arrangements are in place, there will be proportionally fewer older people in residential aged care. Those who do go are likely to be more disabled and have greater care needs. And those with more money will pay more for their accommodation and everyday living arrangements. But they may have more choice too.

    Although the federal government has ruled out an aged care levy and changes to assets test on the family home, it has yet to respond to the majority of the recommendations. But given the aged care minister chaired the taskforce, it’s likely to provide a good indication of current thinking.The Conversation

    Hal Swerissen, Emeritus Professor, La Trobe University

    This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  • Can Home Tests Replace Check-Ups?

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    It’s Q&A Day at 10almonds!

    Have a question or a request? You can always hit “reply” to any of our emails, or use the feedback widget at the bottom!

    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

    ❝I recently hit 65 and try to get regular check-ups, but do you think home testing can be as reliable as a doctor visit? I try to keep as informed as I can and am a big believer in taking responsibility for my own health if I can, but I don’t want to miss something important either. Best as a supplemental thing, perhaps?❞

    Depends what’s being tested! And your level of technical knowledge, though there’s always something to be said for ongoing learning.

    • If you’re talking blood tests, urine tests, etc per at-home test kits that get sent off to a lab, then provided they’re well-sourced (and executed correctly by you), they should be as accurate as what a doctor will give, since they are basically doing the same thing (taking a sample and sending it off to a lab).
    • If you’re talking about checking for lumps etc, then a dual approach is best: check yourself at home as often as you feel is reasonable (with once per month being advised at a minimum, especially if you’re aware of an extra risk factor for you) and check-ups with the doctor per their recommendations.
    • If you’re talking about general vitals (blood pressure, heart rate, heart rate variability, VO₂ max, etc), then provided you have a reliable way of testing them, then doing them very frequently at home, to get the best “big picture” view. In contrast, getting them done once a year at your doctor’s could result in a misleading result, if you just ate something different that day or had a stressful morning, for example.

    Enjoy

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  • Sugar, Hazelnuts, Books & Brains

    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.

    It’s Q&A Day!

    Each Thursday, we respond to subscriber questions and requests! If it’s something small, we’ll answer it directly; if it’s something bigger, we’ll do a main feature in a follow-up day instead!

    So, no question/request to big or small; they’ll just get sorted accordingly

    Remember, you can always hit reply to any of our emails, or use the handy feedback widget at the bottom. We always look forward to hearing from you!

    Q: Interesting info, however, I drink hazelnut milk LOL so would have liked a review of that. But now I want to give hemp and pea milks a try. Thanks

    Aww! Here then just for you, is a quick rundown…

    • Pros: high in protein¹, vitamin B, and vitamin E
    • Cons: high in fat², low in calcium

    ¹Compared head-to-head with almond milk for example, it has double the protein (but also double the calories)

    ²However, is also has been found to lower LDL (bad) cholesterol (and incidentally, also reduce inflammation), and in a later systematic review, it was found to not correlate to weight gain, despite its high calorie-content.

    If you don’t already, and would like to try making your own…

    Click here for step-by-step instructions to make your own hazelnut milk! (very simple)

    Q: Wondering if you can evaluate CLA and using it to assist with weight loss. Thanks

    Will do! (Watch this space)

    Q: What’s the process behind the books you recommend? You seem to have a limitless stream of recommendations

    We do our best!

    The books we recommend are books that…

    • are on Amazon—it makes things tidy, consistent, and accessible. And if you end up buying one of the books, we get a small affiliate commission*.
    • we have read—we would say “obviously”, but you might be surprised how many people write about books without having read them.
    • pertain in at least large part to health and/or productivity.
    • are written by humans—bookish people (and especially Kindle Unlimited users) may have noticed lately that there are a lot of low quality AI-written books flooding the market, sometimes with paid 5-star reviews to bolster them. It’s frustrating, but we can tell the difference and screen those out.
    • are of a certain level of quality. They don’t have to be “top 5 desert-island books”, because well, there’s one every day and the days keep coming. But they do have to genuinely deliver the value that we describe, and merit a sincere recommendation.
    • are varied—we try to not give a run of “samey” books one after another. We will sometimes review a book that covers a topic another previously-reviewed book did, but it must have something about it that makes it different. It may be a different angle or a different writing style, but it needs something to set it apart.

    *this is from Amazon and isn’t product-specific, so this is not affecting our choice of what books to review at all—just that they will be books that are available on Amazon.

    Q: Great video on dopamine. Thumbs up on the book recommendation. Would you please consider doing a piece or two on inflammation? I live with Lupus and it is a constant struggle. Thanks for the awesome work you do. Have an excellent day.

    Great suggestion! We will do that, and thank you for the kind words!

    Q: Why is your newsletter called 10almonds? Maybe I missed it in the intro email, but my curiosity wants to know the significance. Thanks!”

    It’s a reference to a viral Facebook hoax! There was a post going around that claimed:

    ❝HEADACHE REMEDY. Eat 10–12 almonds, the equivalent of two aspirins, next time you have a headache❞ ← not true!

    It made us think about how much health-related disinformation there was online… So, calling ourselves 10almonds was a bit of a tongue-in-cheek reference to that story… but also a reminder to ourselves:

    We must always publish information with good scientific evidence behind it!

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  • Alzheimer’s: The Bad News And The Good

    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.

    Dr. Devi’s Spectrum of Hope

    This is Dr. Gayatri Devi. She’s a neurologist, board-certified in neurology, pain medicine, psychiatry, brain injury medicine, and behavioral neurology.

    She’s also a Clinical Professor of Neurology, and Director of Long Island Alzheimer’s Disease Center, Fellow of the American Academy of Neurology, and we could continue all day with her qualifications, awards and achievements but then we’d run out of space. Suffice it to say, she knows her stuff.

    Especially when it comes to the optimal treatment of stroke, cognitive loss, and pain.

    In her own words:

    ❝Helping folks live their best lives—by diagnosing and managing complex neurologic disorders—that’s my job. Few things are more fulfilling! For nearly thirty years, my focus has been on brain health, concussions, Alzheimer’s and other dementias, menopause related memory loss, and pain.❞

    ~ Dr. Gayatri Devi

    Alzheimer’s is more common than you might think

    According to Dr. Devi,

    ❝97% of patients with mild Alzheimer’s disease don’t even get diagnosed in their internist offices, and half of patients with moderate Alzheimer’s don’t get diagnosed.

    What that means is that the percentage of people that we think about when we think about Alzheimer’s—the people in the nursing home—that’s a very, very small fraction of the entirety of the people who have the condition❞

    ~ Dr. Gaytatri Devi

    As for what she would consider the real figures, she puts it nearer 1 in 10 adults aged 65 and older.

    Source: Neurologist dispels myths about Alzheimer’s disease

    Her most critical advice? Reallocate your worry.

    A lot of people understandably worry about a genetic predisposition to Alzheimer’s, especially if an older relative died that way.

    See also: Alzheimer’s, Genes, & You

    However, Dr. Devi points out that under 5% of Alzheimer’s cases are from genetics, and the majority of Alzheimer’s cases can be prevented be lifestyle interventions.

    See also: Reduce Your Alzheimer’s Risk

    Lastly, she wants us to skip the stigma

    Outside of her clinical practice and academic work, this is one of the biggest things she works on, reducing the stigma attached to Alzheimer’s both publicly and professionally:

    Alzheimer’s Disease in Physicians: Assessing Professional Competence and Tempering Stigma

    Want more from Dr. Devi?

    You might enjoy this interview:

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    And here’s her book:

    The Spectrum of Hope: An Optimistic and New Approach to Alzheimer’s Disease and Other Dementias – by Dr. Gayatri Devi

    Enjoy!

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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 2020

    Cannabis-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 2017

    Interaction 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.

    This article first appeared on The Journalist’s Resource and is republished here under a Creative Commons license.

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