Despite being consumed by humans for thousands of years, cannabis remains a somewhat mysterious plant. The same joint that may ease one person into a soothing state of euphoria could jolt another into a hellish panic attack.

Complicating matters is the plant’s outlaw status. It remains federally illegal in the United States, deemed a Schedule 1 substance in the same category as heroin, requiring special permission from the Drug Enforcement Agency (DEA) to use in studies.

Despite the U.S. federal government’s strict stance, several American states have gone rogue and permitted recreational use, and even more states are considering it.

Canada will legalize recreational use nation-wide on October 17 and several other countries like Chile, Italy, Jamaica, Argentina, Uruguay, and Colombia, have either decriminalized or legalized both medical and recreational use.

With many parts of the world shifting away from criminalizing cannabis, studies related to the plant are now being regularly conducted, with sometimes surprising and contradictory results.

As part of our Marijuana Files coverage, CityNews has delved into the wealth of established and emerging research on the topic. Here’s five interesting takeaways from our deep dive into marijuana, with links to 50 studies that shed new light on the physical, psychological, and societal effects of cannabis consumption. (Click the title for links)

1. Marijuana could help regulate your weight

For some, marijuana is synonymous with the munchies. The drug’s appetite-stimulating properties are the butt of countless stoner jokes. But it’s no laughing matter for people suffering from wasting illnesses, or going through chemotherapy treatments. So, does marijuana really cause weight gain? A 2014 report by Innovations in Clinical Neuroscience found that marijuana may indeed stimulate the appetite and aid in weight gain for people suffering from illnesses or undergoing cancer treatments, but in the general population, cannabis use is actually associated with a lower body mass index. The takeaway: Marijuana may help regulate a healthy body weight. “Marijuana may genuinely be a regulatory compound, increasing weight in those with low weight, but not in those who are normal or overweight,” the study concludes.

2. Marijuana use has negligible effect on crime

Back in the Reefer Madness days, citizens were led to believe that a single toke of marijuana had the potential to transform a formerly law-abiding citizen into a raging, homicidal maniac. That sensational depiction may have been debunked, but there are still concerns that marijuana will lead to more crime. Not so, says a 2018 study by Victoria University of Wellington and Motu Economic and Public Policy Research. In fact, they found that violent crimes and property crimes fell by 20 per cent in California after the state permitted medical marijuana usage. “We also find no evidence that heavy marijuana users commit property crime to fund addictions,” the study concluded. “Our results suggest that liberalization of marijuana laws is unlikely to result in the substantial social cost that some politicians clearly fear.

3. Weed won’t turn you in Michael Phelps

Olympic swimming sensation Michael Phelps may be one of the greatest athletes ever known to hit the bong, but don’t expect your own weed smoking habits to lead you to Olympic glory. That’s the conclusion from a study by the Clinical Journal of Sport Medicine. It found “no evidence of performance-enhancing” effects when it came to athletes and weed. But marijuana could help athletes in different ways. “Cannabis use has also recently been identified as helping athlete’s sleep time and recovery, which may favor performance when an athlete is facing multiple competitions in a short period,” the study notes.

4. More weed, more sex?

So we’ve established that weed won’t make you a better athlete, but it could make you more active between the sheets according to research by The Journal of Sexual Medicine. It set out to study if there was a relationship between marijuana use and sexual frequency. Despite the stereotype that stoners are lazy, they seem to be quite energetic when it comes to sex. The study’s conclusion: “A positive association between marijuana use and sexual frequency is seen in men and women across all demographic groups.”

5. Potential treatment for autism?

Can cannabis help treat autism spectrum disorder (ASD)? A study published in the journal Neurology sought to find out if compounds found in the cannabis plant could improve behavioural problems in children with autism. In the study, 60 children with autism were treated with oral CBD and TCH at a ratio of 20:1. The results were promising. Behavioral outbreaks, anxiety and communication problems, and disruptive behaviors were all markedly improved. Conclusion: “This preliminary study supports the feasibility of CBD based medical cannabis as a promising treatment option for refractory behavioral problems in children with ASD.”

More marijuana studies:

6. Gone to Pot – A Review of the Association between Cannabis and Psychosis

In individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. Several factors appear to moderate these associations, including family history, genetic factors, history of childhood abuse, and the age at onset of cannabis use. Exposure to cannabinoids in adolescence confers a higher risk for psychosis outcomes in later life and the risk is dose-related.

7. Cannabinoids and psychosis

Cannabinoids can induce acute transient psychotic symptoms or an acute psychosis in some individuals. What makes some individuals vulnerable to cannabinoid-related psychosis is unclear. Also clear is that cannabinoids can also exacerbate psychosis in individuals with an established psychotic disorder, and these exacerbations may last beyond the period of intoxication. Less clear is whether cannabis causes a persistent de novo psychosis.

8. Opposite Cannabis-Cognition Associations in Psychotic Patients Depending on Family History

In a sample of 268 first-episode psychosis patients and 237 controls. We found that cannabis use was associated with worse working memory, regardless of family history. However, cannabis use was clearly associated with worse cognitive performance in patients with no family history of psychosis, in cognitive domains including verbal memory, executive function and global cognitive index, whereas cannabis users with a family history of psychosis performed better in these domains.

9. Effects of marijuana on memory

Working Memory Paradigm: A Meta-Analysis of Normative Functional Neuroimaging Studies the n-back task, in which subjects are asked to monitor the identity or location of a series of verbal or nonverbal stimuli and to indicate when the currently presented stimulus is the same as the one presented n trials previously. We conducted a quantitative meta-analysis of 668 sets of activation coordinates in Talairach space reported in 24 primary studies of n-back task variants manipulating process (location vs. identity monitoring) and content (verbal or nonverbal) of working memory.

10. Affect and cannabis use in daily life: a review and recommendations for future research

Findings support a negative reinforcement hypothesis for clinical samples in terms of general NA and anger/hostility. However, discrepancies among studies point to a need to thoroughly characterize samples, consider motives for and expectancies of use, improve quantification of cannabis use, and consider co-use with other substances. Additional design recommendations are also offered for future studies.

11. Medicinal Properties of Cannabinoids, Terpenes, and Flavonoids in Cannabis, and Benefits in Migraine, Headache, and Pain: An Update on Current Evidence and Cannabis Science.

There is accumulating evidence for various therapeutic benefits of cannabis/cannabinoids, especially in the treatment of pain, which may also apply to the treatment of migraine and headache. There is also supporting evidence that cannabis may assist in opioid detoxification and weaning, thus making it a potential weapon in battling the opioid epidemic.

12. GWAS of lifetime cannabis use reveals new risk loci, genetic overlap with psychiatric traits, and a causal influence of schizophrenia.

Abstract: Cannabis use is a heritable trait that has been associated with adverse mental health outcomes. In the largest genome-wide association study (GWAS) for lifetime cannabis use to date (N = 184,765), we identified eight genome-wide significant independent single nucleotide polymorphisms in six regions.

13. A Modern Conundrum for the Pediatrician: The Safety of Breast Milk and the Cannabis-Using Mother

Despite this cautionary evidence, cannabis is now the most commonly reported recreational drug used by pregnant and lactating women. Up to 36% of women report having used marijuana at some point in their pregnancy, and 18% report having used it while breastfeeding.2 These high rates of reported use raise important issues for those medical providers who provide care to infants and children or who may be asked by parents about the safety of marijuana use during lactation

14. Cannabidiol for Epilepsy: New Hope on the Horizon?

There has been an enormous interest in developing antiepileptic drugs with novel mechanisms of action. This review discusses the evidence supporting the anticonvulsant properties of cannabis in humans, focusing on cannabidiol.

15. Development of simple and accurate detection systems for Cannabis sativa using DNA chromatography

This study was aimed to establish a simple and accurate cannabis DNA detection system using DNA chromatography.

16. Adverse Effects of Cannabis on Male Reproduction

Abstract: The use of cannabis use is likely to increase as regulations on its consumption are diminishing throughout the world. Coinciding with an increase in the use of cannabis is an observation that semen quality appears to be declining in developed countries, and couples are delaying conception more often than previous generations

17. Motives for and impairment associated with alcohol and marijuana use among college students

Analyses indicated that among alcohol-only users, social motives predicted more alcohol use, while among dual users, enhancement motives predicted more alcohol and marijuana use and impairment. Coping motives predicted more marijuana use among dual users, but not more alcohol use. Frequency of alcohol and marijuana use predicted more impairment across both the alcohol-only and dual users

18. Leveraging methodology from research on tobacco, alcohol, and opioid analgesics to make rapid and policy-relevant advances in cannabis science

The legalization of medical and recreational cannabis use has occurred ahead of science. The current evidence base has poor utility for determining if cannabis products can meet the standards of safety, efficacy, and quality intrinsic to modern medicine, and for informing regulation of cannabis as a legal intoxicant.

19. Comparing medical and recreational cannabis use among employees: associations with health and work-related outcomes

Nearly one in five US employees reports having used cannabis in the past year. As policies and laws regarding cannabis use rapidly change, concerns have arisen over employees’ use of cannabis, for both medical and recreational purposes.

20. Marijuana Use, Marijuana Expectancies, and Hypersexuality among College Students

The current study examined links between marijuana lifetime use and hypersexuality among university students

21. Marijuana use and risky sexual behavior among high-risk adolescents: trajectories, risk factors, and event-level relationships

Adolescents involved with the juvenile justice system have a high incidence of risky sexual behaviors resulting in unintended pregnancy and sexually transmitted infections. Substance use may be particularly important as a risk factor for unsafe sexual behavior for this group, and recent evidence suggests a possible association between marijuana use and risky sexual behavior.

22. Relative influence of perceived peer and family substance use on adolescent alcohol, cigarette, and marijuana use across middle and high school

This study examined trends in concordance of adolescent cigarette, alcohol and marijuana use and corresponding perceived use by friends and family members during middle and high school.

23. Fast extraction of cannabinoids in marijuana samples by using hard-cap espresso machines

A simple, quick and low cost procedure was developed for the extraction of Δ9-tetrahydrocannabinol, cannabidiol, and cannabinol from marijuana samples, based on the use of a hard-cap espresso extraction with 2-propanol.

24. The potential of near infrared spectroscopy to estimate the content of cannabinoids in Cannabis sativa L.: A comparative study

The aim of the present research was to develop a fast, economical, robust and environmentally friendly method based on NIR technology that allow the quantification of the main cannabinoids present in Cannabis sativa

25. An epidemiological, developmental and clinical overview of cannabis use during pregnancy

Cannabis use in pregnancy poses major health concerns for pregnant mothers and their developing children. Although studies on the short- and long-term consequences of prenatal cannabis exposure are increasing, findings have been inconsistent or difficult to interpret due to methodological issues.

26. Cannabis in liver disorders: a friend or a foe?

In this review, we evaluate the available evidence on cannabis and its constituents and the application of this evidence in clinical practice, focusing particularly on the liver and liver diseases.

27. Exploring cannabis concentrates on the legal market: User profiles, product strength, and health-related outcomes

Concentrate users endorsed higher symptoms of cannabis use disorder and use higher strength cannabis even when using non-concentrated forms. Frequent use of concentrates may be associated with additional risks over and above frequent use of flower forms.

28. The association between physical pain and cannabis use in daily life: An experience sampling method.

Experiences of pain are not associated with decisions about whether or not to use cannabis. Once cannabis users are in cannabis-using situations, they tend to use larger amounts when they are experiencing elevated levels of pain. This may have implications for cannabis abuse treatment as pain may make it more difficult for users to reduce their consumption.

29. Ability to monitor driving under the influence of marijuana among non-fatal motor-vehicle crashes: An evaluation of the Colorado electronic accident reporting system.

States, including Colorado, could consider standardization of drug testing and mandatory reporting policies for drivers involved in motor-vehicle crashes and proactively address the narrow window of time for sample collection to improve DUI of marijuana surveillance. Practical applications: The evaluation of state motor-vehicle crash systems’ ability to capture crashes involving drug impaired driving (DUID) is a critical first step for identifying frequency and risk factors for crashes related to DUID.

30. Acute renal (kidney) infarction induced by heavy marijuana smoking

Acute renal infarction usually occurs in patients with severe atherosclerosis or valvular heart disease. We here report a 42-year Saudi male who presented with severe abdominal pain nausea and vomiting associated with hematuria, after heavy smoking of marijuana.

31. GWAS of lifetime cannabis use reveals new risk loci, genetic overlap with psychiatric traits, and a causal influence of schizophrenia

Cannabis use is a heritable trait that has been associated with adverse mental health outcomes. In the largest genome-wide association study (GWAS) for lifetime cannabis use to date (N = 184,765), we identified eight genome-wide significant independent single nucleotide polymorphisms in six regions.

32. Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk

CONCLUSIONS: 9-THC was measurable in a majority of breast milk samples up to 6 days after maternal marijuana use.

33. Marijuana Use During Pregnancy and Breastfeeding: Implications for Neonatal and Childhood Outcomes

Marijuana is one of the most widely used substances during pregnancy in the United States. Emerging data on the ability of cannabinoids to cross the placenta and affect the development of the fetus raise concerns about both pregnancy outcomes and long-term consequences for the infant or child.

34. Development of simple and accurate detection systems for Cannabis sativa using DNA chromatography

This study was aimed to establish a simple and accurate cannabis DNA detection system using DNA chromatography. Two chromatography chip systems with different features were successfully developed

35. Cannabinoid concentrations in blood and urine after smoking cannabidiol joints

In this study, we investigated cannabinoid blood and urine concentrations of a naive user and of a modeled chronic user after smoking a single CBD joint. Chronic use was modeled as smoking 2 joints per day for 10 days.

36. Adverse Effects of Cannabis on Male Reproduction

The use of cannabis use is likely to increase as regulations on its consumption are diminishing throughout the world. Coinciding with an increase in the use of cannabis is an observation that semen quality appears to be declining in developed countries, and couples are delaying conception more often than previous generations.

37. Long-term consequences of adolescent cannabis exposure on the development of cognition, brain structure and function: an overview of animal and human research

Evidence from both animal and human studies suggests that the severity of the effects of cannabis use on cognitive development is dependent on the age when cannabis use begins. One possible explanation is that those who begin cannabis use early in adolescence are more likely to become heavily dependent.

38. Gender-specific relationships between depressive symptoms, marijuana use, parental communication and risky sexual behavior in adolescence

A large body of research has identified correlates of risky sexual behavior, with depressive symptoms and marijuana use among the most consistent psycho-social predictors of sexual risk

39. Cannabinoid concentrations in blood and urine after smoking cannabidiol joints

In Switzerland, the sale of cannabis with tetrahydrocannabinol (THC) content less than 1% has recently been legalized. As a consequence, cannabis with low THC and high cannabidiol (CBD) values up to approximately 25% is legally available on the market. In this study, we investigated cannabinoid blood and urine concentrations of a naive user and of a modeled chronic user after smoking a single CBD joint.

40. Cannabis use and mental health in young people: cohort study

OBJECTIVE: To determine whether cannabis use in adolescence predisposes to higher rates

41. Assessing the effects of medical marijuana laws on marijuana use: the devil is in the details

This paper sheds light on previous inconsistencies identified in the literature regarding the relationship between medical marijuana laws (MMLs) and recreational marijuana use by closely examining the importance of policy dimensions (registration requirements, home cultivation, dispensaries) and the timing of when particular policy dimensions are enacted.

42. Prevalence of marijuana and other substance use before and after Washington State’s change from legal medical marijuana to legal medical and nonmedical marijuana: Cohort comparisons in a sample of adolescents.

This exploratory study found that marijuana use was more prevalent among teens shortly after the transition from medical marijuana legalization only to medical and nonmedical marijuana legalization, although the difference between cohorts was not statistically significant.

43. Marijuana Use, Recent Marijuana Initiation, and Progression to Marijuana Use Disorder Among Young Male and Female Adolescents Aged 12-14 Living in US Households

Our study used 2005-2014 data from the annual, cross-sectional National Survey on Drug Use and Health to study the prevalence and correlates of marijuana initiation, use, and marijuana use disorder (MUD; abuse or dependence) among 12- to 14-year olds living in civilian US households (n = 84 954). Examined correlates included age, sex, race/ethnicity, poverty status, metropolitan status, year of survey, depression, tobacco use, alcohol use, and fighting at school.

44. Cannabidiol as a Therapeutic Alternative for Post-traumatic Stress Disorder: From Bench Research to Confirmation in Human Trials

Since the discovery of the involvement of the endocannabinoid (eCB) system in emotional memory processing, pharmacological manipulation of eCB signaling has become a therapeutic possibility for the treatment of PTSD.

45. Effect of Vaporized Cannabis on Exertional Breathlessness and Exercise Endurance in Advanced COPD: A Randomized Controlled Trial.

Single-dose inhalation of vaporized cannabis had no clinically meaningful positive or negative effect on airway function, exertional breathlessness and exercise endurance in adults with advanced COPD.

46. The effects of medical marijuana laws on cannabis-involved driving

This study uses data from the Fatality Analysis Reporting System and a differences-in-differences model to examine the effect of state medical marijuana laws (MMLs) on cannabis-involved driving among U.S.

47. Antidepressant-like effect induced by Cannabidiol is dependent on brain serotonin levels

Cannabidiol (CBD) is a compound of Cannabis sativa with relevant therapeutic potential in several neuropsychiatric disorders including depression. CBD treatment has shown significant antidepressant-like effects in different rodent preclinical models. However, the mechanisms involved in CBD-induced antidepressant effects are still poorly understood.

48. Prevalence and associated birth outcomes of co-use of Cannabis and tobacco cigarettes during pregnancy

Use of Cannabis and use of tobacco overlap, and co-use of Cannabis and tobacco has increased over the past decade among adults. The current study aims to document the prevalence and correlates of co-use of Cannabis and tobacco cigarettes among adult pregnant women.

49. Associations Between Marijuana Use and Involuntary Job Loss in US-representative longitudinal and cross-sectional samples

OBJECTIVE: To investigate whether marijuana use is associated with involuntary job loss.

50. Associations between marijuana use and tobacco cessation outcomes in young adults.

Marijuana and tobacco co-use is common among young adults, and findings are mixed regarding the association between marijuana use and smoking cessation outcomes. This study examined the longitudinal relationships between marijuana use and smoking cessation outcomes among young adults.