Browse more cannabis research, findings, methods, and limitations.
A review of 52+ studies found cannabis impairs driving but blood THC levels do not reliably predict impairment, creating a fundamental challenge for per se driving laws.
In nearly 8,000 hepatitis C patients, cannabis use had no effect on cure rates regardless of opioid substitution therapy status, removing a barrier to treating substance-using patients.
A survey found 7.5% of Ontario apartment residents were involuntarily exposed to cannabis smoke from neighbors, similar to tobacco smoke exposure (6.6%), with lower-income residents most affected.
A large multi-site study found only cannabis-dependent users, not regular non-dependent users, showed smaller hippocampi, regardless of dose, suggesting dependence involves unique brain changes.
A balanced review found cannabis is associated with multiple health harms but causal evidence is largely missing, while cannabinoid-based drugs show legitimate therapeutic potential across many conditions.
A review found cannabinoid receptors modulate dopamine, serotonin, noradrenaline, GABA, glutamate, and opioid systems, explaining the broad spectrum of cannabis effects on mental health.
Adolescent synthetic cannabinoid users had thinner frontal cortex than controls, with ADHD comorbidity producing additional brain changes, suggesting interactive effects on the developing brain.
A cannabinoid and serotonin drug synergistically prevented seizures in rats when combined, though neither worked alone, revealing a novel CB1/5-HT2B anti-seizure interaction.
A controlled study found a single low IV dose of THC caused symptoms in 94% of healthy volunteers, with women experiencing significantly more negative effects and all physical reactions.
Among 232 Italian cancer patients, 81% knew about medical cannabis but only 2% learned from healthcare professionals, while 34% had considered using it, revealing a clinician communication failure.
Antipsychotic-naive psychosis patients with recent cannabis use showed more excitement symptoms initially but responded better to treatment at 10 weeks, suggesting a potentially more treatable psychosis subtype.
Cannabis-using youth showed weaker frontostriatal brain circuit activation during cognitive conflict tasks, suggesting self-regulation circuit changes appear early in the course of cannabis use.
A review found growing evidence for cannabis-based treatments in CDKL5 Deficiency Disorder, including an open-label trial showing seizure reduction, building on proven CBD efficacy in similar severe epilepsies.
A review found MS patients commonly use cannabis for symptoms but avoid discussing it with nurses due to stigma, highlighting a communication gap that undermines person-centered care.
Animal study showing THC and synthetic cannabinoids suppress substance P-induced vomiting through CB1 receptor activation, helping explain why cannabinoids work against nausea resistant to standard treatments.
Review of evidence suggesting CBD has antipsychotic properties through a unique non-dopamine mechanism, potentially offering a new treatment class for psychotic disorders with fewer side effects.
Large veteran study found co-occurring opioid and cannabis use disorders linked to fewer opioid prescriptions but higher psychiatric admissions and homelessness compared to opioid use disorder alone.
Narrative review of animal studies showing CBD reduces alcohol consumption, motivation to drink, and relapse while protecting against alcohol-related liver and brain damage.
Literature review describing cannabinoid hyperemesis syndrome, an under-diagnosed condition causing cyclic vomiting in chronic cannabis users, with complete cessation as the only known cure.
Study of 120 patients identifies Can s 3 as the main cannabis allergen in up to 72% of anaphylaxis cases, with cross-reactivity to other plant foods, and evaluates five diagnostic approaches.
Genome-wide study of over 350,000 people identifies CHRNA2, a nicotinic receptor gene, as the first replicated genetic risk factor for cannabis use disorder, linking it to cholinergic and cognitive pathways.
Retrospective study of 1,661 psychiatric inpatients found synthetic cannabinoid users didn't have longer stays or need higher antipsychotic doses than cannabis users, while both groups had shorter stays than non-drug users.
National propensity-matched study of over 7,000 IBD hospitalizations found cannabis users had shorter stays, lower charges, and lower colorectal cancer rates, though some complications were higher.
Across 11 European cities, daily high-potency cannabis use was linked to ~5x higher odds of first-episode psychosis, with population impact varying by local market potency.
Systematic review of 15 studies finds no current roadside oral fluid test for cannabis meets the 80% accuracy standard, though devices detecting lower THC levels showed better performance.
Review exploring how combined alcohol and cannabis exposure alters gene activity through epigenetic mechanisms across different life stages, with potential for lasting and even intergenerational effects.
Review showing cannabinoids cross the placenta and may impair fetal immune development through cytokine disruption, lymphoid cell death, and epigenetic changes with potentially lifelong consequences.
Colorado grocery store data shows OTC sleep aid sales dropped sharply after recreational dispensaries opened, with a 236% trend reversal driven by substitution away from antihistamine-based sleep products.
Review identifying at least 13 deaths and 35 serious cardiovascular emergencies linked to cannabis use, plus multiple strokes and vascular arteritis cases, likely underestimating the true incidence.
Five-year study of 7,717 opioid treatment patients found persistent heroin use strongly predicted crack cocaine co-use but was associated with less cannabis escalation, with crack being the key predictor of treatment failure.
Roadside testing of 2,355 Washington drivers found daytime THC-positive rates tripled after recreational sales opened, while risk perceptions and self-reported use remained unchanged.
Systematic review of 23 studies finds moderate-certainty evidence that pharmaceutical CBD reduces seizure frequency by about 20% in children with drug-resistant epilepsy, with diarrhea as the main side effect.
Comprehensive review finding CBD has established efficacy for epilepsy, early clinical signals for anxiety and psychosis, and preclinical-only evidence for depression and Alzheimer's.
Longitudinal study of 4,975 young men found ADHD predicted persistent risky alcohol and nicotine use but was associated with maturing out of risky cannabis use over 15 months.
Meta-analysis of 18 trials shows CB1 receptor blockers consistently caused diarrhea and GI symptoms, suggesting potential repurposing for constipation-predominant IBS if psychiatric side effects can be avoided.
Female rats showed greater CB1 receptor changes than males after identical THC exposure across all brain regions. Estradiol contributed to the difference.
Study of 366 young LA cannabis users found self-reported medical use linked to less illicit drug use, while concentrate and edible use predicted more other drug use, regardless of frequency.
Controlled study of 40 MS patients found 28 days of cannabis abstinence produced significant improvements in every cognitive measure tested, with corresponding increases in brain activation on fMRI.
Analysis of the landmark ABCD study found prenatal cannabis exposure associated with increased psychosis proneness in children, especially when mothers continued use after knowing they were pregnant.
Washington State analysis found marijuana arrests dropped dramatically after legalization, but the relative disparity between African American and White arrest rates doubled from 2.5x to 5x.
Study of 500 college students finds the MAOA gene interacts with childhood abuse to predict cannabis and tobacco use in sex-opposite patterns: high-activity variants matter in women, low-activity in men.
Canadian Rheumatology Association finds zero clinical trials and insufficient evidence for cannabis in joint diseases, but issues pragmatic guidance acknowledging widespread patient use.
Mouse study shows depression-induced pain amplification involves changes in brain endocannabinoid levels, and locally boosting endocannabinoids reduced the heightened pain response only in depressed animals.
Observational study of 18 autism patients found CBD-rich cannabis extract (75:1 CBD:THC) improved symptoms in 14 of 15 who completed 6-9 months of treatment, with strongest gains in seizures, ADHD, sleep, and social interaction.
Comprehensive review of FDA-approved CBD for epilepsy details its efficacy in severe childhood epilepsies, complex pharmacokinetics including a 4x food effect, and important drug interaction with clobazam that may partly explain its benefits.
Across 30 European countries, cannabis resin potency doubled while cost per milligram of THC dropped from 2006 to 2016 — users got more THC for less money.
Lancet Neurology review finds strong RCT evidence for CBD in severe childhood epilepsies and some cannabis treatments for MS, but no demonstrated benefit for Huntington's, ADHD, or dementia.
Review of cannabinoid-based addiction treatments finds promising newer strategies including neutral CB1 antagonists, CB2 agonists, and CBD after the rimonabant setback, with some entering clinical trials.
Study of 5,622 Canadian youth found depression, anxiety, and drug disorders linked to being out of school and work, but cannabis use disorder showed no association at all.
Twin study of 2,007 young adults finds non-medical painkiller misuse shares moderate genetic overlap with cannabis and nicotine use, but minimal overlap with cannabis or alcohol use disorders.