All In Your Head (Which Is Where It’s Supposed To Be)
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Today’s news is all about things above the neck, and mostly in the brain. From beating depression to beating cognitive decline, from mindfulness against pain to dentistry nightmares to avoid:
Transcranial ultrasound stimulation
Transcranial magnetic stimulation is one of those treatments that sounds like it’s out of a 1950s sci-fi novel, and yet, it actually works (it’s very well-evidenced against treatment-resistant depression, amongst other things). However, a weakness of it is that it’s difficult to target precisely, making modulation of most neurological disorders impossible. Using ultrasound instead of a magnetic field allows for much more finesse, with very promising initial results across a range of neurological disorders
Read in full: Transcranial ultrasound stimulation: a new frontier in non-invasive brain therapy
Related: Antidepressants: Personalization Is Key!
This may cause more pain and damage, but at least it’s more expensive too…
While socialized healthcare systems sometimes run into the problem of not wanting to spend money where it actually is needed, private healthcare systems have the opposite problem: there’s a profit incentive to upsell to more expensive treatments. Here’s how that’s played out in dentistry:
Read in full: Dentists are pulling healthy and treatable teeth to profit from implants, experts warn
Related: Tooth Remineralization: How To Heal Your Teeth Naturally
Mindfulness vs placebo, for pain
It can be difficult with some “alternative therapies” to test against placebo, for example “and control group B will merely believe that they are being pierced with needles”, etc. However, in this case, mindfulness meditation was tested as an analgesic vs sham meditation (just deep breathing) and also vs placebo analgesic cream, vs distraction (listening to an audiobook). Mindfulness meditation beat all of the other things:
Read in full: Mindfulness meditation outperforms placebo in reducing pain
Related: No-Frills, Evidence-Based Mindfulness
Getting personal with AI doctors
One of the common reasons that people reject AI doctors is the “lack of a human touch”. However, human and AI doctors may be meeting in the middle nowadays, as humans are pressed to see more patients in less time, and AI is trained to be more personal—not just a friendlier affect, but also, such things as remembering the patient’s previous encounters (again, something with which overworked human doctors sometimes struggle). This makes a big difference to patient satisfaction:
Read in full: Personalization key to patient satisfaction with AI doctors
Related: AI: The Doctor That Never Tires?
Combination brain therapy against cognitive decline
This study found that out of various combinations trialled, the best intervention against cognitive decline was a combination of 1) cognitive remediation (therapeutic interventions designed to improve cognitive functioning, like puzzles and logic problems), and 2) transcranial direct current stimulation (tDCS), a form of non-invasive direct brain stimulation, similar to the magnetic or ultrasound methods we mentioned earlier today. Here’s how it worked:
Read in full: Study reveals effective combination therapy to slow cognitive decline in older adults
Related: How To Reduce Your Alzheimer’s Risk
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Eat Real Food and Love It – by Kari McCloskey
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Half the battle of healthy eating is enjoying it—because once you do, it’s no longer a battle!
So that’s what this book focuses on. The author, a Registered Nutritionist, does indeed dispense nutritional advice, as you might expect, but also bids us pay attention to what nature’s foods do for us, and notice what less healthy foods take from us. She goes through these category by category, quite comprehensively, before moving on to the more “active” parts of the book.
There’s a lot about training our senses, and about taking a holistic approach to eating, as well as renewing not just our relationship with food, but also various other parts of our life that are inextricably linked to it (from sleep and exercise, to social considerations, and medical issues that healthier eating will help us to avoid or at least tame).
The style is… Joyful. Much like this reviewer, the author loves food, and it shows. She also (again much like this reviewer) cares deeply about the impact food has on her, and (for a third time: like this reviewer!) wants to share that joy and care with the reader. The priority is readability and helpfulness; scientific references are still provided wherever appropriate, though.
Bottom line: if you’d like to improve your eating but it seems like a chore, this book can help turn it into an excitingly enjoyable journey instead.
Click here to check out Eat Real Food And Love It, and eat real food and love it!
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Machine-Dispensed Coffee & Heart Health
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We have written before about the health benefits (and risks) of coffee; for most people, the benefits far outweigh the risks, but individual cases may vary:
The Bitter Truth About Coffee (or is it?) ← this is a mythbusting edition
Speaking of bitterness; coffee has abundant polyphenols, which means…
- Coffee is the world’s biggest source of antioxidants
- 65% reduced risk of Alzheimer’s for coffee-drinkers
- 67% reduced risk of type 2 diabetes for coffee-drinkers
- 43% reduced risk of liver cancer for coffee-drinkers
- 53% reduced suicide risk for coffee-drinkers
See also: Why Bitter Is Better: Enjoy Bitter Foods For Your Heart & Brain ← while it says foods in the title, this does cover coffee too.
For mythbusting on caffeine specifically, enjoy: Caffeine: Cognitive Enhancer Or Brain-Wrecker?
There are also gut health benefits from drinking coffee, and what’s good for our gut is invariably good for our heart and brain:
Coffee & Your Gut ← gut bacteria do not, by the way, have a preference about how you make your coffee or whether it is caffeinated or not
The latest science on coffee and heart health
Specifically, on coffee and cholesterol levels, so for a quick primer on cholesterol, check out: Demystifying Cholesterol
High total cholesterol, and especially high LDL (“bad” cholesterol) is generally associated with cardiovascular disease, for the reasons outlined in the link above.
Recently, researchers at Uppsala University in Sweden examined the levels of cafestol and kahweol, which are both diterpenes, substances known to increase cholesterol levels, in coffee made by various methods, including those dispensed from coffee machines in workplaces.
Two samples were taken from each machine every 2–3 weeks, and the most common kinds of machines produced the highest concentrations of diterpenes. These machines are the ones that push hot water through a small amount of ground coffee, through a wide-gauge filter, dispensing coffee into a cup in about 30 seconds.
Actual espresso machines, which work on the same principle but usually with a finer filter, higher pressure, and slower dispensing of the drink, had widely varying results, quite possibly because there is (in most machines) a human element in how tightly the ground coffee is packed into the metal filter basket.
Simple filter coffee, whether made in a coffee percolator machine or made using the pour-over method, had the lowest concentrations of diterpenes.
You can read about this study here:
However!
We were curious as to how, exactly, cafestol and kahweol increase cholesterol levels.
It turns out that research in this area has been scant, because most mice aren’t affected by it in the way that most humans are, which has limited mouse model studies.
Scant does not mean non-existent, though, and the answer came by virtue of transgenic mice (specifically, apolipoprotein (apo) E*3-Leiden transgenic mice, which do have the same reaction to cafestol as humans), the paper title sums it up nicely:
You may be wondering: what does suppression of bile acid synthesis have to do with cholesterol levels?
To oversimplify it a bit: cafestol messes with cholesterol metabolism by interfering with the enzymes involved in cholesterol metabolism (specifically, regulatory enzymes found in bile acid).
As to what it actually does in that regard: it reduces LDLR (LDL receptor) mRNA levels by 37% (that figure’s an average of the specific enzymes, sterol 27-hydroxylase and oxysterol 7α-hydroxylase, which were reduced by 32% and 48%, respectively).
Why this matters in practical terms: cafestol does not add any cholesterol to our systems, it inhibits our ability to clear LDL cholesterol, thus promoting raised LDL cholesterol levels.
In other words: if you have little or no dietary cholesterol (no dietary cholesterol, for example, if you are vegan), then your body will only have the cholesterol that it made for itself because it needed it, and as such, the body won’t need to do the same kind of clean-up job that it would if you had that coffee with a double cheeseburger with extra bacon.
As such, if you have little or no dietary cholesterol, cafestol is unlikely to have anything like the same effect on cholesterol levels.
Disclaimer: this latter is technically a hypothesis, but based on sound reasoning:
It’s the same logic that says “if you do not drink alcohol, then eating a durian fruit, which inhibits aldehyde dehydrogenase, which the body uses to metabolize alcohol, will not cause alcohol-related problems for you”.
Want to know more?
We wrote previously on coffee and cafestol, along with some suggestions:
Health-Hack Your Coffee To Make Your Coffee Heart-Healthier!
Enjoy!
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Mythbusting Moldy Food
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Most Food Should Not Be Fuzzy
In yesterday’s newsletter, we asked you for your policy when it comes to mold on food (aside from intentional mold, e.g. blue cheese etc), and the responses were interesting:
- About 49% said “throw the whole thing away no matter what it is; it is dangerous”
- About 24% said “cut the mold off and eat the rest of whatever it is”
- The remainder were divided equally between “eat it all; keep the immune system on its toes” and “cut the mold off bread, but moldy animal products are dangerous”
So what does the science say?
Some molds are safe to eat: True or False?
True! We don’t think this is contentious so we’ll not spend much time on it, but just for the sake of being methodical: foods that are supposed to have mold on, including many kinds of cheese and even some kinds of cured meat (salami is an example; that powdery coating is mold).
We could give a big list of safe and unsafe molds, but that would be a list of names and let’s face it, they don’t introduce themselves by name.
However! The litmus test of “is it safe to eat” is:
Did you acquire it with this mold already in place and exactly as expected and advertised?
- If so, it is safe to eat (unless you have an allergy or such)
- If not, it is almost certainly not safe to eat
(more on why, later)
The “sniff test” is a good way to tell if moldy food is bad: True or False?
False. Very false. Because of how the sense of smell works.
You may feel like smell is a way of knowing about something at a distance, but the only way you can smell something is if particles of it are physically connecting with your olfactory receptors inside you. Yes, that has unfortunate implications about bathroom smells, but for now, let’s keep our attention in the kitchen.
If you sniff a moldy item of food, you will now have its mold spores inside your respiratory system. You absolutely do not want them there.
If we cut off the mold, the rest is safe to eat: True or False?
True or False, depending on what it is:
- Hard vegetables (e.g carrots, cabbage), and hard cheeses (e.g. Gruyère, Gouda) – cut off with an inch margin, and it should be safe
- Soft vegetables (e.g. tomatoes, and any vegetables that were hard but are now soft after cooking) – discard entirely; it is unsafe
- Anything else – discard entirely; it is unsafe
The reason for this is because in the case of the hard products mentioned, the mycelium roots of the mold cannot penetrate far.
In the case of the soft products mentioned, the surface mold is “the tip of the iceberg”, and the mycelium roots, which you will not usually be able to see, will penetrate the rest of it.
“Anything else” seems like quite a sweeping statement, but fruits, soft cheeses, yogurt, liquids, jams and jellies, cooked grains and pasta, meats, and yes, bread, are all things where the roots can penetrate deeply and easily. Regardless of you only being able to see a small amount, the whole thing is probably moldy.
The USDA has a handy downloadable factsheet:
Molds On Food: Are They Dangerous?
Eating a little mold is good for the immune system: True or False?
False, generally. There are of course countless types of mold, but not only are many of them pathogenic (mycotoxins), but also, a food that has mold will usually also have pathogenic bacteria along with the mold.
See for example: Occurrence, Toxicity, and Analysis of Major Mycotoxins in Food
Food poisoning will never make you healthier.
But penicillin is safe to eat: True or False?
False, and also penicillin is not the mold on your bread (or other foods).
Penicillin, an antibiotic* molecule, is produced by some species of Penicillium sp., a mold. There are hundreds of known species of Penicillium sp., and most of them are toxic, usually in multiple ways. Take for example:
Penicillium roqueforti PR toxin gene cluster characterization
*it is also not healthy to consume antibiotics unless it is seriously necessary. Antibiotics will wipe out most of your gut’s “good bacteria”, leaving you vulnerable. People have died from C. diff infections for this reason. So obviously, if you really need to take antibiotics, take them as directed, but if not, don’t.
See also: Four Ways Antibiotics Can Kill You
One last thing…
It may be that someone reading this is thinking “I’ve eaten plenty of mold, and I’m fine”. Or perhaps someone you tell about this will say that.
But there are two reasons this logic is flawed:
- Survivorship bias (like people who smoke and live to 102; we just didn’t hear from the 99.9% of people who smoke and die early)
- Being unaware of illness is not being absent of illness. Anyone who’s had an alarming diagnosis of something that started a while ago will know this, of course. It’s also possible to be “low-level ill” often and get used to it as a baseline for health. It doesn’t mean it’s not harmful for you.
Stay safe!
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How To Recover Quickly From A Stomach Bug
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How To Recover Quickly From A Stomach Bug
Is it norovirus, or did you just eat something questionable? We’re not doctors, let alone your doctors, and certainly will not try to diagnose from afar. And as ever, if unsure and/or symptoms don’t go away or do get worse, seek professional medical advice.
That out of the way, we can give some very good general-purpose tips for this one…
Help your immune system to help you
So far as you can, you want a happy healthy immune system. For the most part, we’d recommend the following things:
Beyond Supplements: The Real Immune-Boosters!
…but you probably don’t want to be exercising with a stomach bug, so perhaps sit that one out. Exercise is the preventative; what you need right now is rest.
Hydrate—but watch out
Hydration is critical for recovery especially if you have diarrhea, but drinking too much water too quickly will just make things worse. Great options for getting good hydration more slowly are:
- Peppermint tea
- (peppermint also has digestion-settling properties)
- Ginger tea
- See also: Ginger Does A Lot More Than You Think
- Broths
- These will also help replenish your sodium and other nutrients, gently. Chicken soup for your stomach, and all that. A great plant-based option is sweetcorn soup.
- By broths, we mean clear(ish) water-based soups. This is definitely not the time for creamier soups.
❝Milk and dairy products should be avoided for 24 to 48 hours as they can make diarrhea worse.
Initial dietary choices when refeeding should begin with soups and broth.❞
Source: American College of Gastroenterology
Other things to avoid
Caffeine stimulates the digestion in a way that can make things worse.
Fat is more difficult to digest, and should also be avoided until feeling better.
To medicate or not to medicate?
Loperamide (also known by the brand name Imodium) is generally safe when used as directed.
Click here to see its uses, dosage, side effects, and contraindications
Antibiotics may be necessary for certain microbial infections, but should not be anyone’s first-choice treatment unless advised otherwise by your doctor/pharmacist.
Note that if your stomach bug is not something that requires antibiotics, then taking antibiotics can actually make it worse as the antibiotics wipe out your gut bacteria that were busy helping fight whatever’s going wrong in there:
- Facing a new challenge: the adverse effects of antibiotics on gut microbiota and host immunity
- Antibiotics as major disruptors of gut microbiota
- Microbiotoxicity: antibiotic usage and its unintended harm to the microbiome
A gentler helper
If you want to give your “good bacteria” a hand while giving pathogens a harder time of it, then a much safer home remedy is a little (seriously, do not over do it; we are talking 1–2 tablespoons, or around 20ml) apple cider vinegar, taken diluted in a glass of water.
❝Several studies indicate apple cider vinegar (ACV)’s usefulness in lowering postprandial glycemic response, specifically by slowing of gastric motility❞
(Slowing gastric motility is usually exactly what you want in the case of a stomach bug, and apple cider vinegar)
See also:
- Antimicrobial activity of apple cider vinegar against Escherichia coli, Staphylococcus aureus and Candida albicans
- Antibacterial apple cider vinegar eradicates methicillin resistant Staphylococcus aureus and resistant Escherichia coli
Take care!
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Passion Fruit vs Blueberries – Which is Healthier?
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Our Verdict
When comparing passion fruit to blueberries, we picked the passion fruit.
Why?
It wasn’t close!
In terms of macros, the passion fruit has 3x the protein, 1.5x the carbs, and more than 4x the fiber. An easy win for passion fruit!
In the category of vitamins, passion fruit has more of vitamins A, B2, B3, B5, B6, B7, B9, C, and choline, while blueberries have more of vitamins B1, E, and K. So, blueberries are not without their merits, but all in all, another win for passion fruit here.
When it comes to minerals, passion fruit has more calcium, copper, iron, magnesium, manganese, phosphorus, potassium, and selenium, while blueberries have slightly more zinc.
Looking at polyphenols, this is one category where blueberry wins, and by a fair margin. We think that’s a great reason to enjoy blueberries, but not enough to reverse the win for passion fruit based on all the other categories!
Want to learn more?
You might like to read:
What’s Your Plant Diversity Score?
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 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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