Explore study breakdowns, from what researchers found to the limitations behind each conclusion.
Extended daily THC use reversed typical heart rate increases, instead slowing heart rate and lowering blood pressure through apparent sympathetic nervous system suppression.
Money incentives partially reduced cannabis-induced cognitive impairment, while experienced users showed no behavioral tolerance advantage over first-time users.
Chronic marijuana smokers had lower active T-lymphocyte counts than non-smokers, with 39% falling below the normal range, while B-cell levels remained unaffected.
Marijuana reduced eye pressure only in users who experienced relaxation and a substantial high, suggesting an indirect mechanism rather than a direct drug effect.
THC injection suppressed macrophage migration inhibition factor in immunized rats, with peak suppression at 15 hours, suggesting a mechanism for cannabis-related immune changes.
Marijuana smoke reduced lung immune cell bacteria-killing from 78% to 11% in a dose-dependent pattern. The toxic component was in the gas phase, not THC.
THC suppressed antibody-producing spleen cells and reduced overall spleen cellularity in immunized mice, suggesting broad immune suppression effects.
In a landmark NEJM trial, oral THC prevented chemotherapy vomiting in 80% of completed courses versus 0% for placebo, with no vomiting during subjective highs.
Chronic marijuana smokers had normal total T-cell counts but impaired T-cell function, suggesting cannabis alters immune cell behavior rather than reducing cell numbers.
Marijuana and amphetamine produced additive cardiovascular effects but psychomotor impairment came only from marijuana, with no stimulant counteraction.
Alcohol impaired smooth eye tracking at multiple doses. Cannabis produced no measurable effect on the same visual tracking tasks in experienced users.
Combining cannabis with dextroamphetamine produced impairment similar to cannabis alone. The stimulant did not counteract cannabis-related motor deficits.
Twelve adults smoked cannabis daily for 64 days under hospital observation. Immune function markers remained normal or improved throughout the study period.
Among 1,689 Egyptian men, cannabis users showed cognitive deficits compared to non-users, but the gap was smallest among illiterate, rural, and older participants.
Four youths injected boiled cannabis-seed tea intravenously. All developed shock, organ damage, and bleeding. All survived but the reactions were potentially fatal.
A 1978 medical review identified cannabis as promising for glaucoma and asthma but flagged cardiovascular risks during exercise and preliminary concerns about lung and immune effects.
A 1981 critical review found THC showed promise against chemotherapy nausea but identified significant gaps in safety and pharmacological knowledge.
California designed a four-protocol statewide program to study THC dosing for cancer nausea across ages, involving over 200 investigators and including children and elderly patients.
Data from 120 subjects showed cannabis tolerance develops and fades quickly, while withdrawal symptoms including insomnia, irritability, and tremor appeared after as few as 7 days of use.
THC eye drops lowered eye pressure in animals but not in six glaucoma patients. Researchers concluded THC likely reduces eye pressure systemically, not locally.
A double-blind trial found 10 mg oral THC significantly reduced muscle spasticity. Tonic spasms responded well, but cerebellar disease did not.
A historical review traced how federal laws, patient reports, and 25 state research acts moved THC from prohibition into active medical investigation by 1981.
An opiate receptor blocker inhibited THC-induced pain relief, temperature changes, tolerance, and dependence in rats, suggesting cannabis and opiates share brain pathways.
A cannabis derivative performed similarly to standard medication for preventing radiation-induced vomiting. Both drugs were well tolerated with no clear winner.
In 214 cancer patients, THC and prochlorperazine were equally effective against chemotherapy nausea. THC had more side effects, but patients tolerated them and those effects correlated with nausea relief.
A 1983 review found THC outperformed placebo and standard drugs for chemotherapy nausea, with effectiveness linked to the "high." Synthetic cannabinoids nabilone and levonantradol offered additional options.
A screening of 32 cannabinoids in rabbits found that certain THC derivatives outperformed THC itself at lowering eye pressure, and non-THC compounds also showed activity.
Among 600 drivers killed in single-vehicle crashes, alcohol was detected in 79.3% at high levels. THC was found in only 7.8%, and most drug-positive drivers also had high blood alcohol.
Five cannabis-naive volunteers tested positive for THC in blood and urine after 30 minutes of passive exposure to cannabis smoke in a closed car.
A 1985 review assessed medical cannabis evidence for nausea, glaucoma, and MS spasticity, noting that barriers to use were primarily moral and ethical rather than scientific.
Five dystonia patients improved 20-50% on oral CBD up to 600 mg/day, but two with coexisting Parkinson's features experienced worsened tremor and slowed movement.
A major 1986 pharmacological review found cannabis's greatest health concern was its impact on youth development, while finding no proven brain damage and limited physical dependence in adults.
THC suppressed human natural killer cell activity against tumor cells in lab tests at concentrations as low as 5 micrograms/mL. The effect was dose- and time-dependent.
A cancer patient developed a dangerous lung fungal infection while using illicitly obtained marijuana during chemotherapy, highlighting contamination risks for immunocompromised users.
Smoking cannabis measurably improved both muscle spasticity and hand tremor in an MS patient, confirmed by clinical rating, EMG, and electromagnetic recording.
Molecular modeling showed that the orientation of the C9 substituent relative to a hydroxyl oxygen determined whether cannabinoid compounds were psychoactive or inactive.
In mice, THC suppressed immune cell proliferation differently depending on age and tissue type. Adult thymus cells and young splenocytes were most affected.
Mice processed synthetic THC variants similarly to natural THC, with the 11-oic acid metabolite dominating at about 95% of total metabolism for one variant.
CBD at approximately 700 mg/day for six weeks showed no significant benefit for Huntington's Disease symptoms in 15 patients, but was well tolerated with no toxicity.
Oral CBD at 700 mg/day produced mean plasma levels of only 5.9-11.2 ng/mL with a 2-5 day elimination half-life. No THC was detected, confirming CBD does not convert to THC.
A survey of over 1,000 oncologists found 44% had recommended illegal marijuana to chemo patients, with a majority favoring prescription availability. They rated smoked marijuana more effective than oral dronabinol.
Chronic cannabis extract boosted specific liver enzymes in rats, including a 3-fold increase in carcinogen-activating AHH. Most effects reversed within a week of stopping.
Animal studies showed chronic THC altered the hippocampus in rats, but required at least 3 months of exposure in young animals. Monkey studies did not consistently replicate these findings.
Brain recordings showed long-term cannabis users processed irrelevant information that non-users filtered out, indicating impaired attentional resource allocation.
A 1992 review found that despite widespread human use, animals would not self-administer THC and evidence of brain reward pathway stimulation was minimal. The newly discovered cannabinoid receptor was opening new research directions.
The 1992 discovery of anandamide — the brain's own cannabis-like molecule — proving the endocannabinoid system exists and launching an entirely new field of neuroscience.
Among New York young adults, early alcohol use (ages 13-16) was the strongest predictor of later marijuana and cigarette use, supporting an age-dependent gateway pattern.
Computational modeling identified a "receptor essential volume" near the cannabinoid receptor that explains why some cannabinoid compounds bind effectively while others cannot.
Among 1,481 heavy smokers trying to quit with nicotine patches, marijuana users had half the odds of success. Early lapse (3+ cigarettes in first 4 weeks) predicted relapse in 96%.
A 1994 oncologist survey ranked marijuana ninth among antiemetics, with estimated 50% efficacy and 25% adverse effects. Only 6% would prescribe more even if it were legal.