Browse more cannabis research, findings, methods, and limitations.
Vomiting-related ER visits in Colorado rose 29% from 2013 to 2018, with each additional recreational dispensary linked to a 3% increase, though areas with existing medical dispensaries saw slower growth.
Most rigorous meta-analysis of cannabis for chronic pain: 32 trials, 5,174 patients. Real but modest benefit — NNT ~24 with manageable side effects.
Prospective study of 46 adults using real-time smartphone assessments found medical cannabis reduced pain intensity, anxiety, depression, and improved sleep over 3 months.
Three-year MRI study found heavy cannabis users showed accelerated cerebellar thickening in regions linked to cognition and motor control, with changes tied to earlier onset of cannabis use.
First study of developmental CBD exposure found mice exposed in utero and during nursing showed increased anxiety and thousands of brain DNA methylation changes as adults, despite known benefits of direct CBD exposure.
Prospective study found CHS in 1.6% of patients with unexplained abdominal pain at two French EDs. CHS patients spent 70% more time in the ED and visited nearly twice as often.
Large longitudinal study of 4,535 cigarette smokers found no evidence that cannabis use inhibits quitting cigarettes, with similar quit rates across never, former, and current cannabis users.
Animal study found THC's primary metabolite (11-OH-THC) was 7-31 times more potent than THC in mice, with female rats significantly more sensitive to THC than males.
Study of 517 hospitalized patients with schizophrenia found cannabis use was not independently associated with longer hospital stays or more frequent admissions after adjusting for covariates.
Multi-state ecologic study found recreational cannabis legalization was associated with a 15% increase in fatal motor vehicle collisions and 16% increase in traffic deaths.
Study of 301 cannabis-using young adults found those most influenced by legalization attitudes reported the heaviest use and highest problematic cannabis use scores.
Small study of 16 older adults found chronic cannabis users had higher fall risk, worse balance, and slower walking speed than matched non-users, though cognitive function was similar.
Survey of 1,034 college students found higher cannabis use was associated with more hallucinations (independent of depression) and delusional ideation that was more distressing and held with greater conviction.
Survey of 568 adults 65+ found 15% used cannabis, with most starting after 60 for medical purposes (mainly pain), yet only 41% told their healthcare provider.
Canadian study found accidental cannabis ingestions increased 77% in children after legalization, despite no overall change in pediatric ER visit volume when accounting for pre-existing trends.
Study of 55 CHS patients found capsaicin cream did not shorten ER stays overall, but patients receiving it within the first two treatment rounds were discharged significantly faster (4.8 vs. 7.1 hours).
Mouse study found a CB2 cannabinoid receptor agonist protected against fentanyl-induced respiratory depression without affecting breathing on its own, confirmed through knockout mice.
Study of 368 chronic migraine patients found cannabis users had 6.3 times higher odds of medication overuse headache, with 81% of cannabis users affected vs. 41% of non-users.
Analysis of 10,644 adolescent drug users found two-thirds started with marijuana, with a 40% probability of transitioning to other drugs by year 8, lower than the 70-80% rate for those starting with other substances.
Mendelian randomization found no broad causal link between cannabis use and cardiovascular disease, but after adjusting for tobacco and BMI, possible small effects on small vessel stroke (17% increase) and atrial fibrillation (6% increase) emerged.
Oral fluid drug tests matched urine results well across drug classes. Cannabis was detectable with a shorter detection window — potentially better for measuring recent use.
Survey of 817 cannabis users found quality, strain type, price, THC content, and pesticide status drive purchase decisions, with medical users prioritizing CBD and pesticides over THC.
Systematic review of 21 studies found adolescent CHS follows adult diagnostic patterns but may be more common in females, with 21% having comorbid mood disorders and cannabis cessation as the only effective treatment.
Danish study of 78 children with severe epilepsy found CBD reduced seizures by 50%+ in 31% at 3 months, with Dravet/Lennox-Gastaut patients responding best (70%). Response declined to 20% at 24 months.
Large Canadian cohort study found medical cannabis patients had 44% higher risk of ER visits or hospitalization for heart attack or stroke, with the association strongest in males (77% higher risk).
Pilot RCT of 30 stage IV cancer patients found medical cannabis via state program was feasible, well-tolerated, and showed trends toward reduced opioid use and better pain control.
Prospective cohort found marijuana-only use in pregnancy was linked to 66% higher risk of small birth size and 126% higher risk of very small birth size, independent of tobacco exposure.
Small RCT of 50 type 2 diabetes patients found a CBD-dominant sublingual spray significantly reduced total cholesterol and HbA1c over 8 weeks with no serious adverse effects.
Web-based cannabis reduction program reduced use by 11.5 days/month in adults with ADHD symptoms, with significant improvements in depression, anxiety, and ADHD symptom severity at 3 months.
Analysis of 15,238 US adults found starting cannabis before age 15 was associated with 4.4 times higher odds of lifetime suicide attempt and 3.3 times higher odds of suicidal ideation.
A 27-year-old with no traditional risk factors had a heart attack after cannabis use, showing significant coronary artery narrowing requiring stent placement.
Study of 68 type 1 diabetes patients found cannabis users presenting with apparent DKA had dramatically different labs (pH 7.42 vs. 7.09), suggesting CHS-related ketosis rather than true DKA.
Three young men with autism developed mania or psychosis after using CBD/THC products, highlighting potential psychiatric risks of cannabis use in the ASD population.
Study of 167 clozapine-treated schizophrenia patients found cannabis use and trauma were associated with psychotic symptoms but not primary negative symptoms, suggesting distinct pathways.
Systematic review of 36 RCTs found cannabinoids better than placebo but not superior to other antiemetics for chemo-induced nausea, leading MASCC to find insufficient evidence for recommending cannabinoids for GI symptoms in cancer.
A 24-year-old with no risk factors developed acute myocarditis with reduced heart function and a blood clot after marijuana use, representing a rare but serious cardiac complication.
CB1 neutral antagonist AM4113 blocked fentanyl discrimination in rats at lower doses and without the side effects of rimonabant, showing promise as a novel approach to opioid use disorder.
Five days of synthetic cannabinoid XLR-11 caused pronounced liver necrosis in mice, driven by oxidative stress, inflammation, and cell death pathways.
Nano-chitosan-coated CBD reduced amyloid plaques, increased brain cannabinoid receptors, and improved memory performance in an Alzheimer rat model.
In first-episode psychosis, cognitive reserve protected against poor outcomes only in non-cannabis users, suggesting cannabis overwhelms the brain's built-in cognitive resilience.
Researchers identified that THC causes dry mouth by activating CB1 receptors on nerve fibers in salivary glands, and CBD dose-dependently reverses this effect.
CHS emergency visits in Alberta doubled after legalization and rose further during COVID-19 (15 to 32 per 100,000). All surveyed CHS patients met criteria for cannabis use disorder.
Open-label study of 18 Tourette patients found medical cannabis reduced tic severity by 38% over 12 weeks, but 40% experienced cognitive side effects and 80% preferred smoking.
Meta-analysis of 19 studies (5,191 participants) found cannabis users had significantly worse formal thought disorder whether healthy, in first-episode psychosis, or with schizophrenia.
Combined RCT data from 40 participants found minimal sex differences in acute vaporized cannabis effects, with males showing only slightly better divided attention and higher metabolite levels.
GRADE-based clinical guidelines found no evidence to recommend any specific antipsychotic for schizophrenia patients with cannabis use disorder, highlighting a critical evidence gap.
Study of 215 Israeli combat veterans found moral injury was linked to cannabis use disorder through depression, with social support unexpectedly failing to protect against this pathway.
Among Israeli combat veterans, depression (AOR 1.98) but not PTSD independently predicted cannabis dependence, challenging assumptions about PTSD-driven cannabis use in military populations.
A survey of 3,805 Italian students found cannabis use at ages 14-15 was associated with a 26-fold higher likelihood of using new psychoactive substances.
A review of CBD science following Malawi's cannabis legalization highlights epilepsy treatment, neuroprotective potential, and a novel proposal for malaria-related brain injury.