Get a Clue - Weed

Details: Published: 04 November 2026; Hits: 5

Cannabis driving fatalities are a problem the research keeps flagging, and the flags are getting harder to ignore. Limit the data to lab confirmed drug use and drivers with cannabis in their system turn up more often among the dead and the injured.

A 2025 systematic review in the International Journal of Drug Policy pooled 31 studies covering 328,388 people. It found a 55% rise in the odds of a fatal crash for drivers with toxicology confirmed cannabis use. The authors put the absolute increase at 14 more deaths per 100,000 collisions. For injuries, the odds doubled.

They rate that evidence as low certainty and say so openly. Low certainty means further research could move the numbers. It does not mean the danger is absent. The main analyses in this debate find added risk, though their authors disagree about how much, and one bias adjusted analysis by White and Burns finds none.

How many cannabis driving fatalities are there each year?
US researchers Kamer and Warshafsky estimate that cannabis related road deaths in America run to about 5,000 a year. That number has been disputed. A commentary by Michael White in the same journal spotted two input errors. The estimate used a wider count of motor vehicle deaths than the traffic count it was meant to cover, and it treated an odds ratio as a relative risk. Fixing both cut the figure to about 3,550.
White then took out every driver who was also over the 0.08 alcohol limit. Using risk values from published meta analyses, his tables still give between roughly 1,800 and 3,200 deaths a year. These are modelled estimates, not a head count, and he stresses the uncertainty. But even his lowest conventional figure is around 1,800 deaths annually.

The roadside data adds weight. US figures cited by White show THC in about 32% of driver fatalities, although roughly 40% of the THC positive drivers were also over the alcohol limit. Sorting out which substance did what is hard. Pretending the cannabis share is zero is harder.

Even the sceptics won’t call it safe
Ole Rogeberg’s 2019 analysis of culpability studies is a favourite of those who want the issue played down. It put the average rise in crash risk at 1.28, with cannabis accounting for under 2% of crashes in most of the studies it covered.

The fine print matters, though. Rogeberg warned that a low average can hide a smaller group of high dose drivers facing much steeper risks. He pointed out that pooled case control studies gave a higher figure of 1.82, and raised the possibility that culpability studies understate the danger. His verdict was clear enough: a low average does not make driving after cannabis use safe, and it does not make cannabis driving fatalities any less real for the families left behind.

Why drivers keep taking the chance
Part of the problem is what people believe. In a 2022 Canadian survey, 21% of adults who use cannabis said they had driven within two hours of using it. The review adds that people who use cannabis are more likely to think it does not impair driving, or even improves it.

Use is also rising. Among Canadians aged 16 and over, past year use climbed from 15% in 2017 to 27% in 2022. More users means more drivers carrying the same false confidence onto the road, which feeds cannabis driving fatalities. Cannabis distorts time, clouds judgement and weakens coordination. Those effects do not suit a vehicle moving at speed, and cannabis related road deaths are where that mismatch ends.

Where bad medicinal cannabis laws fit
The 2025 review says legalisation and the spread of concentrated products have raised both availability and potency. Medicinal schemes are part of that expansion, and too many were drafted with barely a glance at the road.

Look at what the evidence cannot say. The studies in the review did not separate medical from recreational use. Nothing suggests a prescription makes THC safer behind the wheel; the research just cannot tell the two apart. Lawmakers who assume otherwise are guessing, and other people pay when they guess wrong.
Enforcement has its own gaps. There are no standardised THC cut offs for drivers. Impairment can fade within hours, yet THC can stay detectable in blood for at least seven days, in urine for five and in oral fluid for up to 78 hours. Reliable roadside tests are still in development. A medicinal framework that hands out THC products without a tested driving standard leaves a hole, and crashes happen in it.

What the evidence on cannabis driving fatalities demands
The research is rated low certainty, and the direction is consistent. The stakes are fatal, and cannabis related road deaths are not an abstraction. Waiting for perfect proof means burying more people first.

Cannabis driving fatalities deserve the same seriousness as any other form of impaired driving. Governments that loosened the rules, medicinal schemes included, now own the question of what those rules cost on the road. The evidence keeps mounting and defending the status quo gets harder every month.

Dalgarno Institute
Sources

Details: Published: 29 October 2026; Hits: 32

Cannabis and bipolar disorder show a strong link in one of the largest studies of its kind. Researchers followed 463,396 teenagers in Northern California. Those who reported using cannabis in the past year were about twice as likely to be diagnosed with bipolar disorder later on. Their risk of psychosis was higher still.

The study appeared in JAMA Health Forum in February 2026. A team led by Dr Kelly Young Wolff at Kaiser Permanente Northern California carried it out. It lands as cannabis becomes easier to buy and more widely accepted. In 2023, 11.2 per cent of US adolescents aged 12 to 17 reported past year use, the paper notes.

How Researchers Tracked Cannabis and Bipolar Disorder Over Time
Every teenager aged 13 to 17 completed a confidential questionnaire during routine paediatric checkups between 2016 and 2023. One question asked whether they had used marijuana in the past year. At the start, 26,345 of them, or 5.7 per cent, said yes.

The team then followed the group until age 25, or until the end of 2023. Diagnoses came from health records, and the team counted only those made by clinicians. Because teens answered again at later visits, changes in their use counted too. The researchers also adjusted for sex, race and ethnicity, neighbourhood deprivation, insurance type, and alcohol and other substance use.

Bipolar Risk Roughly Doubled for Teens Who Used Cannabis
The numbers on cannabis and bipolar disorder were stark. Teenage cannabis use carried an adjusted hazard ratio of 2.01 for bipolar disorder, which means about double the risk. Psychotic disorders came in at 2.19. Depressive disorders reached 1.34 and anxiety disorders 1.24.
Those figures rest on thousands of diagnoses: 4,061 bipolar, 4,105 psychotic, 62,137 depressive and 73,096 anxiety. The authors say the bipolar result fits earlier research. A meta-analysis they cite found 2.63 times greater odds of bipolar disorder emerging among people who used cannabis. They also stress that any past year use showed the link, not only daily use.

Timing matters for cannabis use and bipolar risk. Bipolar disorder had the longest gap between first reported use and diagnosis, at 2.3 years on average. Cannabis use came first.

Depression and Anxiety Signals Faded With Age
Age made a clear difference for the more common disorders. For depressive disorders, the hazard ratio was 1.78 among 13 to 15 year olds. It fell to 1.35 at ages 16 to 17 and 1.21 at ages 18 to 20. By ages 21 to 25, the link was no longer statistically significant.

Anxiety followed the same path, dropping from 1.47 in the youngest group to 0.95 in the oldest. The authors read this as a sign that adolescence is an especially vulnerable window. THC acts on cannabinoid 1 receptors, and the adolescent brain carries them in high numbers. The paper adds that typical cannabis flower in northern California now exceeds 20 per cent THC.

Could Something Else Explain the Cannabis and Bipolar Disorder Findings?
The researchers tested that question several ways. When they accounted for earlier psychiatric diagnoses, the bipolar hazard ratio stayed high at 1.73. When they removed every teenager with any psychiatric history at baseline, it reached 2.00. Finally, an unmeasured factor would need an association of at least 3.44 with both cannabis use and bipolar disorder to explain the finding away.

The authors still urge caution. No design like this can prove that cannabis causes bipolar disorder. Reverse causation remains possible, since some young people may turn to cannabis to cope with early symptoms before a diagnosis. Use was also self-reported, and the sample came from one insured population in a state where cannabis is legal.

What Cannabis Use and Bipolar Risk Mean for Prevention
The authors argue that the findings back early screening for cannabis at paediatric visits. They also call for stronger public health messaging and policies that limit youth exposure as legalisation spreads. Their list includes more prominent health warnings, stricter enforcement of sales to minors, and tighter rules on packaging, flavours and advertising.

Use was most common among older teens, among Hispanic, Black and White adolescents, and among those on Medicaid or living in more deprived neighbourhoods. The authors say prevention efforts should reach those groups first.

For parents, clinicians and lawmakers, the practical point is plain. Cannabis and bipolar disorder showed one of the two largest signals in the study, alongside psychosis. Delaying or preventing teenage cannabis use looks like a sensible place to start.

(Source: jamanetwork)

Details: Published: 27 October 2026; Hits: 109

Cannabis and alcohol used to sit in separate boxes in the public mind. New American research suggests that line has blurred. Daily cannabis use among parents has quadrupled since 2012. Meanwhile, 49% of past month users of both substances combined them at the same time during their last drinking episode. Together, the findings describe a country where heavy and combined use is starting to look ordinary. That matters, because the student research in this story links perceived norms to how often young people combine the two.

Parents are reaching for cannabis far more often
Researchers analysed the National Survey on Drug Use and Health and found a fourfold rise. Daily cannabis use among parents climbed from 1.3% in 2012 to 5.2% in 2024. By 2024, parents were about four times more likely to use cannabis daily than to drink alcohol daily. That comparison measures frequency, not potency or harm, but the gap ishard to ignore.

In addition, the study tracked parents who use on most days. Among parents living with children, that share rose from 2.6% in 2012 to 8.0% in 2024. News coverage of the study estimated that at least 5.9 million children live with a parent who uses marijuana on most days. However, these figures show how common use is. They do not show whether a child was present during use or exposed to smoke or vapour.

Mixing marijuana and alcohol is now routine
A separate study in JAMA Network Open drew on survey data from 2021 to 2024. Researchers at the National Institute on Drug Abuse found that 49% of adults aged 18 or older who used both marijuana and alcohol in the past month used them simultaneously during their last drinking episode. Instead of swapping one substance for the other, many Americans use both at once.

The pattern was strongest among people with cannabis use disorder. Among those adults, 72.2% of those aged 18 to 29 mixed the two, as did 77.4% of those aged 30 to 49 and 82.0% of those aged 50 or older. The authors pointed to a “normalization of simultaneous use despite potential compounded risks, including impaired judgment, injury, and intoxication effect.” Mixing marijuana and alcohol carries potential compounded risks, and the researchers say so plainly.

Students follow what they believe their peers do
A study in the Journal of American College Health asked 209 college students about alcohol, cannabis and combined use. Every participant had used alcohol only, cannabis only and both in the past year. Students saw alcohol as the most common and most accepted of the three. Yet their beliefs about how common combined use is among peers were the strongest link to how often they combined the two themselves. Beliefs about peer approval showed no link to frequency. Neither type of belief predicted the consequences students reported.

The sample is small, so the findings are a starting point. Still, the authors suggest that interventions could target students’ perceptions of how normal combined use really is. In short, mixing cannabis and alcohol spreads partly because people think everyone else is doing it.

The mental health signals on campus
A survey of 83,467 undergraduates, gathered in 2020 and 2021, tested how alcohol, cannabis and vaping link to depression and anxiety. The sample included 60,746 women and 22,721 men. Researchers compared each group of users with students whose only use was heavy drinking. Students who used both cannabis and vaping devices had the highest odds of depression and anxiety. Among women, the adjusted odds ratios were 1.92 for depression and 1.69 for anxiety. Among men, they were 2.72 and 2.23.

As a result, the picture for students who used cannabis and alcohol alongside vaping is similar, with raised odds. The figures were 1.85 and 1.53 for women and 1.71 and 1.85 for men. The authors noted that the risks were not necessarily additive. These results describe associations, so they cannot prove that use causes either condition. They do show that mixing substances sits alongside poorer mental health in a very large student sample.

What the wider evidence says about homes and laws
Research on legalisation adds another layer. For example, a 2024 longitudinal study pooled three intergenerational samples and linked recreational legalisation to higher teen cannabis use among youth whose parents had used cannabis in their own adolescence. That link did not appear for teens whose parents lacked that history. One systematic review concluded that legalisation tends to increase parental use and approval. It found unclear evidence that legalisation alone worsens parenting or child outcomes, apart from accidental exposures in young children. A national analysis also found no rise in child maltreatment reports after recreational legalisation.

Some caution applies. The parent study relied on surveys that people answered themselves, which can include recall or reporting error. Another parenting study found that children were present in only a small share of use episodes. Even so, clear rules at home, safe storage to keep cannabis away from children, and open talks with teens about expectations remain practical steps while researchers fill the gaps.

The numbers on cannabis and alcohol do not prove harm in every household. They do show that frequent use and mixing have become more visible, and that young people’s habits track what they believe is normal. Overall, adults who set the tone at home and in the community have a say in what that normal looks like.

Dalgarno Institute

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Details: Published: 21 October 2026; Hits: 53

Legal on paper does not mean safe on the job. That blunt message runs through a major legal reference for employers. The drug free workplace facts it sets out deserve a far wider audience.

It all comes from Drug Testing Law, Technology and Practice, February 2026 update, written by David Evans and published by Thomson Reuters on Westlaw. Its chapter on marijuana and the workplace pulls together federal data, medical research and regulator warnings. Read together, they describe a problem that employers can no longer wave away.

Drug Free Workplace Facts Start With a Rising Number
Marijuana produces more positive results on employment drug tests than any other drug, according to the text. It cites the Quest Diagnostics Drug Testing Index, which covered more than 6 million urine tests across the general US workforce. Positivity for marijuana rose from 3.6 per cent in 2020 to 3.9 per cent in 2021. That was an 8.3 per cent jump and the highest rate ever reported in the index.

Stretch the view to five years and the picture is starker. Positivity climbed from 2.6 per cent in 2017 to 3.9 per cent in 2021, a 50 per cent rise.

Impairment Outlasts the High
A joint may be finished in minutes, but the effects linger. The chapter notes that a typical high lasts about two hours. Most behavioural effects return to baseline within three to five hours. Some studies still show residual effects on complex divided attention tasks for up to 24 hours.

The HHS manual for medical review officers, quoted in the text, goes further. It says reduced functional ability lasts at least 4 to 8 hours after a dose. That runs well beyond the point where the user feels the high has gone.

Long term users face a different problem. Even after periods of abstinence, the source reports, selective attention and speed of information processing can stay impaired. An employee can feel fine and still be affected. That gap is one of the drug free workplace facts employers rarely hear.

What It Does to Safety Records
The workplace drug safety facts get harder to ignore once accidents enter the picture. One study of postal workers appears in the chapter. Those who tested positive for marijuana on a pre employment urine test had 55 per cent more industrial accidents. They also had 85 per cent more injuries and 75 per cent greater absenteeism than workers who tested negative.

Bureau of Labor Statistics figures for 2006 to 2020 point the same way. They link recreational marijuana sales to a 10 per cent rise in workplace injuries among employees aged 20 to 34.

Roads tell a similar story. Colorado data in the text show marijuana related traffic deaths more than doubled, from 55 in 2013 to 125 in 2016. The same chapter adds one caution. A large federal study found no significant increase in crash risk traceable to marijuana once driver age, gender, race and alcohol were controlled for. The text says more research is needed.

For commercial drivers, federal rules leave no room for debate. The Department of Transportation states that state legalisation does not change how marijuana is treated under its testing regulations. A driver who uses it is not physically qualified to drive a commercial motor vehicle.

Mental Health Risks Walk Through the Gate Too
Mental health sits inside the drug free workplace facts as well. The text reports that regular use of high potency marijuana raises the risk of psychosis about five times. It also says products today can contain up to 99 per cent THC. Clinical studies of purified THC, it adds, found measurable psychotic symptoms in 40 per cent of people with no family history of psychosis.

The American Psychiatric Association is quoted directly: “There is no current scientific evidence that cannabis is in any way beneficial for the treatment of any psychiatric disorder.” Its statement adds that adolescents are particularly vulnerable. The reason given is the effect of cannabis on neurological development.

The Hemp Loophole at the Corner Shop
Marijuana is only part of the story, and honest drug free workplace facts must cover hemp too. The 2018 Farm Bill was meant to give farmers a new cash crop. Its backers pitched it with the slogan “rope not dope”. Yet a loophole has let chemically derived psychoactive products onto shelves labelled as hemp.

The text calls them derived psychoactive cannabis products. One in six past month cannabis users, or 17 per cent, had used delta 8 THC, the first of them to reach the market.

Dr Matthew Rossheim’s retail survey of the largest hemp chains in Texas, reproduced in the chapter, makes uncomfortable reading. Three chains ran roughly 200 stores. Of those, 58 per cent were not registered with the state health department. Another 38 per cent sat within 1,000 feet of a school or daycare.

Edibles carried up to 15,000 mg of THC per package. States such as California and Oregon cap servings at 10 mg. Some packaging copied well known biscuit and soft drink brands. Staff did not check identification, and every chain handed out free samples. Rossheim rejects the “few bad actors” defence. He writes that these practices are the industry norm, not the exception.

Children are paying for it. Between January 2021 and February 2022, US poison control centres logged 2,362 exposure cases involving delta 8 THC products. Some 41 per cent involved patients under 18, and one paediatric case ended in death. The author argues that the FDA has issued warnings but done very little to protect the public. Seizures, injunctions and prosecutions remain scarce.

The CBD Excuse Does Not Hold Up
Some employees blame CBD when a test comes back positive. Medical review officers do not accept that. For Department of Transportation testing, the text says, CBD use is not a legitimate medical explanation for a laboratory confirmed marijuana result.

Labels are part of the problem, and the workplace drug safety facts on CBD are sobering. FDA sampling in 2020 found that 49 per cent of the 102 products stating a CBD amount contained THC. A JAMA study of 84 samples detected THC in 21 per cent. Just under 31 per cent carried an accurate label. The chapter also describes a truck driver who lost his job after a THC positive test. He had used a product its maker marketed as THC free.

Prevention Starts With a Clear Policy
Employers who act on drug free workplace facts have clear options, and the author’s advice is direct. Policies should make clear that illegal drug use can bring discipline and termination. The same goes for being under the influence of a psychoactive substance. Front line supervisors should learn to spot the signs of substance use. They should also know how to approach an employee who may be endangering themselves or others.

The text argues that testing deters marijuana use. It also says that properly maintaining a drug free workplace reduces employer liability for accidents, injuries and deaths linked to substance use.

Why These Drug Free Workplace Facts Matter
Use is rising and impairment lingers. Injuries follow, and the products keep getting stronger and easier to buy. These drug free workplace facts point to one answer: stop the problem before it reaches the workplace door. Legal status changed on paper, but the risks on the job did not. Those workplace drug safety facts have not changed either.

(Source: WRD News)

Details: Published: 21 October 2026; Hits: 51

Abstract
Cannabis use is a known risk factor for adverse mental health outcomes, including psychosis, which is frequently associated with aggression. However, the specific impact of cannabis use on the risk of violence remains unclear. This meta-analysis, conducted according to PRISMA guidelines, synthesized evidence from 63 peer-reviewed studies (N = 265,079) identified via MEDLINE, EMBASE, and PsycINFO searches up to November 2024 to clarify the link between cannabis use and violence, either as a perpetrator or as a victim. Random-effects models revealed that cannabis users are at a significantly higher risk of perpetrating violent acts. This association was observed in both psychiatric patients (OR 2.49, 95% CI 1.72-3.61) and the general population (OR 2.05, 95% CI 1.74-2.41), and remained significant across both longitudinal (OR 1.17, 95% CI 1.07-1.28) and cross-sectional (OR 2.37, 95% CI 1.66-3.40) study designs. There was an especially large effect for violence involving a criminal conviction in both general (OR 3.75, 95% CI 2.54-5.53) and psychiatric (OR 4.21, 95% CI 2.86-6.22) populations. Furthermore, cannabis use was significantly associated with an increased risk of becoming a victim of violence (OR 1.49, 95% CI 1.38-1.60), a risk more pronounced in females and mixed-gender cohorts compared to males. This meta-analysis indicates an increased risk of violence, especially that resulting in a criminal conviction, among cannabis users. It also highlights the potential of cannabis use as a target for interventions to decrease violence, and underscores the need for routine assessment of cannabis use among psychiatric patients. (

Source: https://pubmed.ncbi.nlm.nih.gov/42779465/)