Recap: Here’s 30 recent studies on the effects of marijuana
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Marijuana could be used to slow the spread of HIV
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In this study researchers found that when treated with a daily dose of THC, monkeys who had an animal form of HIV actually had decreased damaged in the immune tissue of their stomachs over a 17 month period.
“Our results indicate that chronic THC administration modulated duodenal T cell populations, favored a pro-Th2 cytokine balance, and decreased intestinal apoptosis. These findings reveal novel mechanisms that may potentially contribute to cannabinoid-mediated disease modulation.” less
Marijuana use is associated with impaired sleep quality
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A study published by the American Academy of Sleep Medicine found that marijuana use could be associated with difficulty falling asleep, difficulty staying asleep and overall poor quality sleep.
“Results show that any history of cannabis use was associated with an increased likelihood of reporting difficulty falling asleep, struggling to maintain sleep, experiencing non-restorative sleep, and feeling daytime sleepiness. The strongest association was found in adults who started marijuana use before age 15; they were about twice as likely to have severe problems falling asleep (odds ratio = 2.28), experiencing non-restorative sleep (OR = 2.25) and feeling overly sleepy during the day (OR = 1.99). Results were adjusted for potential confounders including age, sex, race/ethnicity and education.” less
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Brain changes are associated with "casual" marijuana use in young adults
In this study, the shape and size of two brain regions that are connected to emotion and motivation were observed to be different between users and non-users. The nucleus accumbens, the reward processing part of the brain, was larger and had an altered shape. The heavier the user, the more significant the change.
However, the study's use of the phrase "casual users" drew heavy criticism, such as this thumping from Slate:
"A press release from the Society for Neuroscience trumpeted the [the] study’s importance because it looked at casual users rather than regular pot smokers, who form the basis of most marijuana studies. That claim is dubious in the extreme. The subjects averaged 3.83 days of smoking and 11.2 total joints per week. Characterizing these people as casual pot smokers was a great media hook, but it defied common sense.
The researchers said: “We collected high-resolution MRI scans on young adult recreational marijuana users and nonusing controls and conducted three independent analyses of morphometry in these structures: (1) gray matter density using voxel-based morphometry, (2) volume (total brain and regional volumes), and (3) shape (surface morphometry). …
These data suggest that marijuana exposure, even in young recreational users, is associated with exposure-dependent alterations of the neural matrix of core reward structures and is consistent with animal studies of changes in dendritic arborization.”
Medical Marijuana: Clearing Away the Smoke
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This study goes into the reasons why marijuana can be used for medical purposes and details why its classification as a schedule I drug blocks progress of research.
“Recent advances in understanding of the mode of action of tetrahydrocannabinol and related cannabinoid in-gredients of marijuana, plus the` accumulating anecdotal reports on potential medical benefits have spurred increasing re-search into possible medicinal uses of cannabis. Recent clinical trials with smoked and vaporized marijuana, as well as other botanical extracts indicate the likelihood that the cannabinoids can be useful in the management of neuropathic pain, spasticity due to multiple sclerosis, and possibly other indications. As with all medications, benefits and risks need to be weighed in recommending cannabis to patients. We present an algorithm that may be useful to physicians in determining whether cannabis might be recommended as a treatment in jurisdictions where such use is permitted.”
Association between Marijuana Exposure and Pulmonary Function over 20 Years
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Marijuana and tobacco smoke may contain many similar components, but this study found that occasional small usage of marijuana had no negative effects on a person’s lungs.
“Occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function.”
“Marijuana smoke contains many of the same constituents as tobacco smoke, but it is unclear whether smoking marijuana causes pulmonary damage similar to that caused by tobacco. …
It is possible that cumulative damage to the lungs from years of marijuana use could be masked by short-term effects; prior analyses have not attempted to disentangle these factors. Smoking marijuana is increasingly common in the United States, and understanding whether it causes lasting damage to lung function has important implications for public health messaging and medical use of marijuana.“
Obesity and Cannabis Use: Results from 2 Representative National Surveys
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In a 2011 French study of marijuana’s effect on weight, the researchers found that people who smoked three times a week were less likely than non-smokers to be obese.
“The adjusted prevalences of obesity in the NESARC and the NCS-R were 22.0% and 25.3%, respectively, among participants reporting no use of cannabis in the past 12 months and 14.3% and 17.2%, respectively, among participants reporting the use of cannabis at least 3 days per week. These differences were not accounted for by tobacco smoking status. Additionally, after adjustment for sex and age, the use of cannabis was associated with body mass index differences in both samples. The authors conclude that the prevalence of obesity is lower in cannabis users than in nonusers.”
Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study
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This study from the British Medical Journal claims that people who started smoking marijuana as an adolescent have a higher chance to develop symptoms of psychosis.
“In individuals who had no reported lifetime psychotic symptoms and no reported lifetime cannabis use at baseline, incident cannabis use over the period from baseline to T2 increased the risk of later incident psychotic symptoms over the period from T2 to T3 (adjusted odds ratio 1.9, 95% confidence interval 1.1 to 3.1; P=0.021). Furthermore, continued use of cannabis increased the risk of persistent psychotic symptoms over the period from T2 to T3 (2.2, 1.2 to 4.2; P=0.016). The incidence rate of psychotic symptoms over the period from baseline to T2 was 31% (152) in exposed individuals versus 20% (284) in non-exposed individuals; over the period from T2 to T3 these rates were 14% (108) and 8% (49), respectively.”
A Population-Based Case-Control Study of Marijuana Use and Head and Neck Squamous Cell Carcinoma
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This study from Cancer Prevention Research found that marijuana users are much less likely to contract head-and-neck squamous-cell carcinoma than non-users.
“After adjusting for potential confounders (including smoking and alcohol drinking), 10 to 20 years of marijuana use was associated with a significantly reduced risk of HNSCC. Among marijuana users moderate weekly use was associated with reduced risk. The magnitude of reduced risk was more pronounced for those who started use at an older. These inverse associations did not depend on human papillomavirus 16 antibody status. However, for the subjects who have the same level of smoking or alcohol drinking, we observed attenuated risk of HNSCC among those who use marijuana compared with those who do not.”
“Our study suggests that moderate marijuana use is associated with reduced risk of HNSCC.”
Respiratory Effects of Marijuana and Tobacco Use in a U.S. Sample
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In this study 5.8 percent of marijuana users had asthma, while only 3.8 percent of non-smokers had asthma. Tobacco smokers came in higher at 6.5 percent.
“Self-reported respiratory symptoms included chronic bronchitis, frequent phlegm, shortness of breath, frequent wheezing, chest sounds without a cold, and pneumonia. A medical exam also provided an overall chest finding and a measure of reduced pulmonary functioning. Marijuana use was associated with respiratory symptoms of chronic bronchitis, coughing on most days, phlegm production, wheezing, and chest sounds without a cold.
The impact of marijuana smoking on respiratory health has some significant similarities to that of tobacco smoking. Efforts to prevent and reduce marijuana use, such as advising patients to quit and providing referrals for support and assistance, may have substantial public health benefits associated with decreased respiratory health problems.”
Cannabis extracts can help stop seizures
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This study from the British Journal of Pharmacology found that cannabis has anticonvulsant effects, making it useful to stop seizures.
“Epilepsy is the most prevalent neurological disease and is characterized by recurrent seizures. Here, we investigate (i) the anticonvulsant profiles of cannabis-derived botanical drug substances (BDSs) rich in cannabidivarin (CBDV) and containing cannabidiol (CBD) in acute in vivo seizure models and (ii) the binding of CBDV BDSs and their components at cannabinoid CB1 receptors. …
CBDV BDSs exerted significant anticonvulsant effects in three models of seizure that were not mediated by the CB1 cannabinoid receptor and were of comparable efficacy with purified CBDV. These findings strongly support the further clinical development of CBDV BDSs for the treatment of epilepsy.”
Cannabis can help slow down brain degeneration
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A study from the Institute of Molecular Psychiatry at the University of Bonn in Germany has found that antioxidants can be released using cannabis which can help remove damaged cells.
“The progression of ageing is largely determined by the balance between detrimental, pro-ageing, largely stochastic processes, and the activity of the homeostatic defense system. Experimental evidence suggests that the cannabinoid system is part of the latter system …
In preclinical models of neurodegenerative disorders, cannabinoids show beneficial effects, but the clinical evidence regarding their efficacy as therapeutic tools is either inconclusive or still missing.”
Marijuana effective against autoimmune disease
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The study showed that THC could alter DNA in a way that would reduce immune functions like chronic inflammation.
“Marijuana is one of the most abused drugs due to its psychotropic effects. Interestingly, it is also used for medicinal purposes. The main psychotropic component in marijuana, Δ9-tetrahydrocannabinol (THC), has also been shown to mediate potent anti-inflammatory properties. …
Together, the current study demonstrates for the first time that THC may modulate immune response through epigenetic regulation involving histone modifications.”
Cancer fighting Cannabinoids that don’t get you high
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Cannabinoids are the chemicals in marijuana that have an effect on your body. There are over 85 of them in marijuana. Some, like THC have psychoactive effects that induce a high, but that is limiting to medical care. This study looked for cannabinoids with medical value that do not get you high. They found six other chemicals in marijuana with no psychoactive effects that fight cancer just as well as THC.
“Cannabinoids are the bioactive components of the Cannabis plant that display a diverse range of therapeutic qualities. We explored the activity of six cannabinoids, used both alone and in combination in leukaemic cells. Cannabinoids were cytostatic and caused a simultaneous arrest at all phases of the cell cycle. Re-culturing pre-treated cells in drug-free medium resulted in dramatic reductions in cell viability. Furthermore, combining cannabinoids was not antagonistic. We suggest that the activities of some cannabinoids are influenced by treatment schedules; therefore, it is important to carefully select the most appropriate strategy in order to maximise their efficacy.”
Using marijuana does not lead to schizophrenia
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A Harvard study has found that there is no link between cannabis use and schizophrenia.
“Cannabis is one of the most highly abused illicit drugs in the world. Several studies suggest a link between adolescent cannabis use and schizophrenia. An understanding of this link would have significant implications for legalization of cannabis and its medicinal value. The present study aims to determine whether familial morbid risk for schizophrenia is the crucial factor that underlies the association of adolescent cannabis use with the development of schizophrenia. …
The results of the current study suggest that having an increased familial morbid risk for schizophrenia may be the underlying basis for schizophrenia in cannabis users and not cannabis use by itself.”
Low doses of THC can help to prevent heart attacks
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Extremely small doses of THC were administered to patients at risk of a heart attack. Researchers found that the THC, even though very little was used, was helpful in protecting against heart attacks when taken up to two days before the attack.
“Tetrahydrocannabinol (THC), the major psychoactive component of marijuana, is a cannabinoid agonist that exerts its effects by activating at least two specific receptors (CB1 and CB2) that belong to the seven transmembrane G-protein coupled receptor (GPCR) family. Both CB1 and CB2 mRNA and proteins are present in the heart. THC treatment was beneficial against hypoxia in neonatal cardiomyocytes in vitro. We also observed a neuroprotective effect of an ultra low dose of THC when applied to mice before brain insults…”
Marijuana could be used as medication for PTSD
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A study out of the New York University School of Medicine found that sufferers of PTSD have more open CB1 receptors in their brains which cannabinoids would be able to help by equaling out the CB1 receptors.
“Endocannabinoids and their attending cannabinoid type 1 (CB1) receptor have been implicated in animal models of post-traumatic stress disorder (PTSD). However, their specific role has not been studied in people with PTSD. Herein, we present an in vivo imaging study using positron emission tomography (PET) and the CB1-selective radioligand [11C]OMAR in individuals with PTSD, and healthy controls with lifetime histories of trauma (trauma-exposed controls (TC)) and those without such histories (healthy controls (HC)). …
These results suggest that abnormal CB1 receptor-mediated anandamide signaling is implicated in the etiology of PTSD, and provide a promising neurobiological model to develop novel, evidence-based pharmacotherapies for this disorder.”
Cannabis can help reduce pain caused by Osteoarthritis
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A study from PLOS One found that CB2 receptors activated by cannabis have the potential for treating people with Osteoarthritis joint pain.
“Osteoarthritis (OA) of the joint is a prevalent disease accompanied by chronic, debilitating pain. Recent clinical evidence has demonstrated that central sensitization contributes to OA pain. An improved understanding of how OA joint pathology impacts upon the central processing of pain is crucial for the identification of novel analgesic targets/new therapeutic strategies. …
These data provide new clinically relevant evidence that joint damage and spinal CB2 receptor expression are correlated combined with converging pre-clinical evidence that activation of CB2 receptors inhibits central sensitization and its contribution to the manifestation of chronic OA pain. These findings suggest that targeting CB2 receptors may have therapeutic potential for treating OA pain.”
Marijuana could reduce symptoms of Crohn’s Disease
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A study out of the Meir Medical Center in Israel researched 21 people with Crohn’s disease that did not respond to conventional treatment. 5 of the 11 people who took THC went into complete remission, while 1 of the 10 who took the placebo did the same.
“The marijuana plant Cannabis sativa has been reported to produce beneficial effects for patients with inflammatory bowel diseases, but this has not been investigated in controlled trials. We performed a prospective trial to determine whether cannabis can induce remission in patients with Crohn's disease …
Although the primary end point of the study (induction of remission) was not achieved, a short course (8 weeks) of THC-rich cannabis produced significant clinical, steroid-free benefits to 10 of 11 patients with active Crohn's disease, compared with placebo, without side effects. Further studies, with larger patient groups and a nonsmoking mode of intake, are warranted.”
Marijuana as a way to fight diabetes
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A study in the American Journal of Medicine has found that consuming marijuana could improve the way your body handles blood sugar, making it a possibly valuable tool for those with diabetes. The study showed the patients who used marijuana had lower levels of insulin which would indicate better control of blood sugar.
“Of the participants in our study sample, 579 were current marijuana users and 1975 were past users. In multivariable adjusted models, current marijuana use was associated with 16% lower fasting insulin levels (95% confidence interval [CI], −26, −6) and 17% lower HOMA-IR (95% CI, −27, −6). We found significant associations between marijuana use and smaller waist circumferences. Among current users, we found no significant dose-response.
We found that marijuana use was associated with lower levels of fasting insulin and HOMA-IR, and smaller waist circumference.”
Driving under the influence of marijuana makes you more likely to crash
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This study from Columbia University found that people who used marijuana within three hours of driving are twice as likely to get into an accident.
“Since 1996, 16 states and the District of Columbia in the United States have enacted legislation to decriminalize marijuana for medical use. Although marijuana is the most commonly detected nonalcohol drug in drivers, its role in crash causation remains unsettled. To assess the association between marijuana use and crash risk, the authors performed a meta-analysis of 9 epidemiologic studies published in English in the past 2 decades identified through a systematic search of bibliographic databases. …
The results of this meta-analysis suggest that marijuana use by drivers is associated with a significantly increased risk of being involved in motor vehicle crashes.”
Marijuana could impair cognitive function in people with multiple sclerosis
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This study from the University of Toronto showed that multiple sclerosis patients who were cannabis users performed worse than non-users in information processing speed, memory, and visual and spatial perception.
“While neuropsychological deficits have been reported in healthy individuals who use street cannabis, data in patients with multiple sclerosis (MS) are lacking. Given that MS is associated with cognitive deterioration, the aim of this study was to determine the neuropsychological effects of cannabis use in this population …
This cross-sectional study provides empirical evidence that prolonged use of inhaled or ingested street cannabis in patients with MS is associated with poorer performance on cognitive domains commonly affected in this population. Whatever subjective benefits patients may derive from using street cannabis (e.g., pain and spasticity relief) should be weighed against the associated cognitive side effects.”
A new study from the University of Sheffeild links marijuana to sperm abnormalities.
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“The study, published in the medical journal Human Reproduction, recruited 2,249 men from 14 fertility clinics around the UK and asked them to fill out detailed questionnaires about their medical history and their lifestyle. …
Men who produced ejaculates with less than four percent normal sperm were nearly twice as likely to have produced a sample in the summer months (June to August), or if they were younger than 30 years old, to have used cannabis in the three month period prior to ejaculation.”
Legal Marijuana does not seem to increase teen use
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A study in the Journal for Adolescent Health using data from the Centers for Disease Control and Prevention has found that legalization of marijuana for medical uses did not increase the rate of use by teens.
The estimation sample was 11,703,100 students. Across years and states, past-month marijuana use was common (20.9%, 95% confidence interval 20.3–21.4). There were no statistically significant differences in marijuana use before and after policy change for any state pairing. In the regression analysis, we did not find an overall increased probability of marijuana use related to the policy change (marginal probability .007, 95% confidence interval −.007, .02).
This study did not find increases in adolescent marijuana use related to legalization of medical marijuana.” less
Alternate method to use marijuana, butane hash oil (dabs), is no more dangerous
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A new study published in Science Direct has found that using dabs does not create more problems or accidents than with traditional flower marijuana.
The present study aimed to gather preliminary information on dabs users and test whether dabs use is associated with more problems than using flower cannabis.
Analyses revealed that using “dabs” created no more problems or accidents than using flower cannabis. Participants did report that “dabs” led to higher tolerance and withdrawal (as defined by the participants), suggesting that the practice might be more likely to lead to symptoms of addiction or dependence.
The use of butane hash oil has spread outside of the medical marijuana community, and users view it as significantly more dangerous than other forms of cannabis use.” less
THC could reduce meth related brain damage
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A study published by the National Institute of Health found that THC can reduce or prevent the effects of brain damage caused by meth abuse.
“Methamphetamine (METH) is a potent psychostimulant with neurotoxic properties. Heavy use increases the activation of neuronal nitric oxide synthase (nNOS), production of peroxynitrites, microglia stimulation, and induces hyperthermia and anorectic effects. Most METH recreational users also consume cannabis. …
Our results indicate that Δ9-THC reduces METH-induced brain damage via inhibition of nNOS expression and astrocyte activation through CB1-dependent and independent mechanisms, respectively.”
Marijuana could help prevent diseases like Alzheimer’s
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The British Journal of Pharmacology published a paper that proposes marijuana could prevent degenerative disorders like Alzheimer’s, Parkinson’s, and Huntington’s disease.
“In an increasingly ageing population, the incidence of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease are rising. While the aetiologies of these disorders are different, a number of common mechanisms that underlie their neurodegenerative components have been elucidated; namely neuroinflammation, excitotoxicity, mitochondrial dysfunction and reduced trophic support. …
This review details the mechanisms of neurodegeneration and highlights the beneficial effects of cannabinoid treatment.”
Consistent cannabis use at a young age could be harmful
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A study from the National Center for Biotechnology Information found that consistent use of marijuana as a child had harmful effects to the individuals IQ as they moved into adulthood.
“Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users …
Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.”
Marijuana could help with depression and self-esteem issues
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A four part study from the University of Kentucky found that users of Marijuana who reported being lonely have higher levels of self-esteem and self-worth.
“Social and physical pain share common overlap at linguistic, behavioral, and neural levels. Prior research has shown that acetaminophen—an analgesic medication that acts indirectly through cannabinoid 1 receptors—reduces the social pain associated with exclusion. Yet, no work has examined if other drugs that act on similar receptors, such as marijuana, also reduce social pain. Across four methodologically diverse samples, marijuana use consistently buffered people from the negative consequences associated with loneliness and social exclusion. These effects were replicated using cross-sectional, longitudinal, and experimental designs. These findings offer novel evidence supporting common overlap between social and physical pain processes.”
Marijuana does not cause aggression
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In January of this year, Addictive Behaviors published a study claiming that while alcohol can increase the odds of aggressive behviour in a person, marijuana did not have any of those effects.
On any alcohol use days, heavy alcohol use days (5 or more standard drinks), and as the number of drinks increased on a given day, the odds of physical and sexual aggression perpetration increased. The odds of psychological aggression increased on heavy alcohol use days only. Marijuana use days did not increase the odds of any type of aggression.
These findings contribute to a growing body of research on the temporal relation between acute alcohol use and IPV perpetration among college men. Combined with previous research, our findings suggest that dating violence intervention and prevention programs should target reductions in alcohol use.” less
CBD can protect against side effects from chemotherapy drugs
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The British Journal of Pharmacology published a study detailing their findings that cannabidiol (CBD) can protect against neurotoxicity and pain that often accompany chemotherapy drugs.
“Background and Purpose
Paclitaxel (PAC) is associated with chemotherapy-induced neuropathic pain (CIPN) that can lead to the cessation of treatment in cancer patients even in the absence of alternate therapies. We previously reported that chronic administration of the non-psychoactive cannabinoid cannabidiol (CBD) prevents PAC-induced mechanical and thermal sensitivity in mice. Hence, we sought to determine receptor mechanisms by which CBD inhibits CIPN and whether CBD negatively effects nervous system function or chemotherapy efficacy.
Conclusions and Implications
Our data suggest that CBD is protective against PAC-induced neurotoxicity mediated in part by the 5-HT1A receptor system. Furthermore, CBD treatment was devoid of conditioned rewarding effects or cognitive impairment and did not attenuate PAC-induced inhibition of breast cancer cell viability. Hence, adjunct treatment with CBD during PAC chemotherapy may be safe and effective in the prevention or attenuation of CIPN.” less
The scientific consensus on marijuana is still up in the air, but it seems to be falling in favor of marijuana with each passing day. In order to provide a survey of the various research that’s been done on the topic, we put together a list of 30 studies about pot use from the past few years.
These studies found both positive and negative outcomes associated with cannabis but show just how the recent scientific findings have started to track with popular opinion — in that more research is finding positive outcomes with marijuana use while the populous is leaning toward legalization just about everywhere.
The most important thing to remember when reading this list is that a large percentage of studies about marijuana are based on correlation — observed conditions in subjects who use or have used marijuana — which makes their validity hard to determine. In fact, the great majority of correlation studies are never proven to be correct. That is, the factors surrounding the condition either include something else that caused the condition or cannot be conclusively reduced to a single cause.
Causation studies on the other hand are much more reliable, because through study design marijuana or other drug can be shown to directly cause an effect. However, these studies are much harder to come by mostly because marijuana is an illegal substance and funding for studies requires the use of cannabis grown for and controlled by the feds, so increases in the number of research projects is muted.