The studies listed below are cited throughout TryCannabis.org and represent some of the most significant cannabis research available. Each entry includes a plain-language summary so you can understand what the study found — and what it means — without needing a science degree.
Major Reviews and Meta-Analyses
These large-scale reviews examine the findings of many individual studies to draw broader conclusions about cannabis and health.
1. Comprehensive Review of 2,500+ Cannabis Studies
Authors: Hsu et al. • Year: 2025 • Journal: JAMA
Strong EvidenceThis landmark review, led by researchers at UCLA Health, analyzed over 2,500 published studies on medicinal cannabis across a wide range of health conditions. The review found that while cannabis shows genuine promise for certain conditions — particularly chronic pain and chemotherapy-related nausea — the evidence remains insufficient for most of the conditions cannabis is commonly marketed for. The authors emphasized that the gap in evidence is partly due to decades of federal restrictions on cannabis research, not necessarily because cannabis is ineffective. This is the single most comprehensive assessment of the cannabis evidence base published to date.
Read Full Study2. Living Review of Cannabis for Pain
Authors: OHSU Research Team • Year: 2025 • Journal: Annals of Internal Medicine
Moderate EvidenceResearchers at Oregon Health & Science University conducted a "living review" — a continuously updated analysis — of cannabis products for chronic pain. The review found that products with higher THC content showed a small but statistically significant reduction in pain, though they also came with more side effects (dizziness, sedation, dry mouth). Importantly, the researchers noted that most available studies were short-term, making it difficult to draw conclusions about long-term use. CBD-only products showed limited evidence for pain relief on their own.
Read Full Study3. Systematic Review of Cannabis for Anxiety Disorders (57 Studies)
Authors: Various • Year: 2025 • Journal: Psychiatry Research (ScienceDirect)
Moderate EvidenceThis systematic review examined 57 individual studies on cannabis and anxiety disorders, including generalized anxiety, social anxiety, and PTSD-related anxiety. The review found a pattern of self-reported benefit among patients, but noted that the evidence is complicated by the biphasic nature of cannabis — low doses tend to reduce anxiety while higher doses can increase it. The authors called for more randomized controlled trials to establish clear dosing guidelines and identify which patients are most likely to benefit.
Read Full StudyCannabis and Opioid Reduction
A growing body of research examines whether cannabis access is associated with reduced opioid use at both individual and population levels.
4. NYS Medical Cannabis Program and Opioid Use
Authors: Slawek et al. • Year: 2025 • Journal: JAMA Internal Medicine
Moderate EvidenceThis study examined patients enrolled in the New York State Medical Cannabis Program who were also taking prescription opioids for chronic pain. Researchers found that patients who used medical cannabis were associated with reductions in opioid use over the study period. While the results are promising, the authors were careful to note that this was an observational study — meaning it shows an association, not proof that cannabis directly caused the reduction. The study underscores the need for randomized controlled trials to confirm these findings.
Read Full Study5. Cannabis Legalization and Opioid Prescriptions
Authors: Lozano-Rojas et al. • Year: 2025 • Institution: University of Georgia
Moderate EvidenceResearchers at the University of Georgia analyzed prescription data in areas where cannabis dispensaries opened and found that the presence of legal cannabis dispensaries was associated with measurable reductions in opioid prescriptions in those communities. This population-level study adds to a growing body of evidence suggesting that cannabis access may serve as an alternative for some patients who would otherwise rely on opioid medications. The study examined prescription patterns rather than individual patient outcomes, so it cannot confirm why prescriptions decreased.
Read Full Study6. Canadian Prospective Study on Opioid Reduction
Authors: Lucas et al. • Year: 2021 • Journal: Pain Medicine
Moderate EvidenceThis Canadian prospective study followed patients who were using both cannabis and opioids for chronic pain over time. The study found that a significant proportion of patients reported reducing their opioid use after incorporating medical cannabis into their pain management regimen. Participants reported improved pain control, better quality of life, and fewer opioid-related side effects. As a prospective observational study, it provides stronger evidence than cross-sectional surveys but does not reach the level of a randomized controlled trial.
Read Full StudyAnxiety
Cannabis and anxiety have a complex relationship. Research suggests effects depend heavily on dosage, cannabinoid profile, and individual factors.
7. Johns Hopkins Cohort Study on Cannabis and Anxiety
Authors: Wolinsky et al. • Year: 2025 • Journal: Journal of Affective Disorders
Moderate EvidenceThis cohort study from Johns Hopkins University followed a group of adults who used cannabis for anxiety-related symptoms over an extended period. Researchers found that participants reported meaningful reductions in anxiety symptoms, with effects that were sustained over time rather than diminishing. However, the study also identified a subset of participants whose anxiety worsened, highlighting that cannabis is not uniformly beneficial for anxiety. The researchers emphasized the importance of appropriate dosing and the need for clinician guidance, particularly for patients new to cannabis.
Read Full Study8. Biphasic Effects of Cannabinoids on Anxiety
Authors: Rey et al. • Year: 2012 • Journal: Neuropsychopharmacology
Strong EvidenceThis foundational study established one of the most important principles in cannabis therapeutics: the biphasic effect. Researchers demonstrated that cannabinoids produce opposite effects at different doses — lower doses tend to reduce anxiety, while higher doses can actually increase it. This finding has shaped modern dosing guidance and is a key reason why the "start low and go slow" approach is considered essential. The study provides a biological explanation for why some people find cannabis calming while others find it anxiety-inducing: the difference often comes down to dose.
Read Full StudyChronic Pain
Pain management is the most widely studied application of medicinal cannabis. See also the OHSU review listed under Major Reviews above.
Endocannabinoid System
Understanding the endocannabinoid system is fundamental to understanding why and how cannabis works in the human body.
9. Review of the Endocannabinoid System
Authors: Lu & Mackie • Year: 2021 • Journal: PMC (Peer-Reviewed)
Strong EvidenceThis comprehensive review details the structure and function of the endocannabinoid system (ECS) — the biological system in every human body that interacts with cannabis compounds. The authors explain how CB1 receptors in the brain and CB2 receptors in immune tissues work, how the body produces its own cannabis-like molecules (endocannabinoids), and how these components work together to maintain homeostasis. The paper provides the scientific foundation for understanding why cannabis can affect such a wide range of bodily functions, from pain perception to mood to immune response.
Read Full Study10. The Endocannabinoid System: Essential and Mysterious
Authors: Harvard Health Publishing • Year: 2021 • Source: Harvard Health Blog
Strong EvidenceThis accessible article from Harvard Health describes the endocannabinoid system as critical for "almost every aspect of our moment-to-moment functioning." It explains how the ECS regulates learning and memory, emotional processing, sleep, temperature control, pain response, inflammatory responses, immune function, and eating. Written for a general audience, it provides an excellent introduction to the science behind why cannabinoid receptors in the brain outnumber many other receptor types and why the ECS is considered one of the most important physiological systems in the body.
Read Full ArticleTerpenes and Entourage Effect
Research into how the many compounds in cannabis work together — rather than in isolation — is a growing area of study.
11. Comprehensive Review of the Entourage Effect
Authors: Various • Year: 2024 • Journal: MDPI Pharmaceuticals
Moderate EvidenceThis review examines the "entourage effect" — the theory that cannabis compounds work synergistically, producing therapeutic effects greater than any single compound alone. The paper evaluates evidence from preclinical and clinical studies showing that combinations of cannabinoids and terpenes may enhance pain relief, reduce inflammation, and modulate anxiety more effectively than isolated compounds. While the concept is widely accepted among cannabis clinicians, the authors note that rigorous clinical evidence is still catching up to the theory, and more human trials are needed to establish which compound combinations are most effective.
Read Full Study12. Terpenes and Cannabinoid Receptors
Authors: Santiago et al. • Year: 2020 • Journal: Frontiers in Pharmacology
Moderate EvidenceThis study investigated whether terpenes — the aromatic compounds responsible for cannabis's distinctive smells — can interact directly with cannabinoid receptors in the body. The researchers found evidence that certain terpenes do modulate cannabinoid receptor activity, suggesting they are not merely responsible for flavor and aroma but may play an active role in the therapeutic effects of cannabis. This research supports the idea that a cannabis product's terpene profile matters for its medicinal effects, not just its THC or CBD content.
Read Full StudyDrug Interactions
Understanding how cannabis interacts with other medications is critical for patient safety, especially for people taking prescription drugs.
13. Cannabinoid Interactions with CYP450 Enzymes
Authors: Doohan et al. • Year: 2021 • Journal: AAPS Journal
Strong EvidenceThis paper examines how cannabinoids — particularly THC and CBD — interact with the CYP450 family of liver enzymes that are responsible for metabolizing the majority of pharmaceutical medications. The researchers found that both THC and CBD can inhibit certain CYP450 enzymes, which means they can potentially increase the blood levels of other medications, leading to stronger effects or increased side effects. This is especially relevant for people taking blood thinners, certain heart medications, anti-seizure drugs, or immunosuppressants. The study underscores why anyone taking prescription medications should consult their healthcare provider before using cannabis.
Read Full Study14. Systematic Review of Cannabis Drug-Drug Interactions
Authors: Bansal et al. • Year: 2024 • Journal: Frontiers in Pharmacology
Moderate EvidenceThis systematic review compiled evidence from multiple studies examining known and suspected drug-drug interactions between cannabis and pharmaceutical medications. The review cataloged specific medication classes with documented interaction risks and assessed the severity of each interaction type. The authors found that while most cannabis-drug interactions are manageable with proper medical oversight, some combinations — particularly with medications that have narrow therapeutic windows — require careful monitoring. The paper serves as a valuable reference for healthcare providers advising patients who use cannabis alongside other medications.
Read Full Study15. Penn State CANN-DIR Drug Interaction Tool
Institution: Penn State University • Type: Interactive Research Tool
CANN-DIR (Cannabis Drug Interaction Resource) is a free, research-backed online tool developed by Penn State University that allows patients and healthcare providers to check for potential interactions between cannabis and specific medications. Users can search by medication name and receive information about known or suspected interactions, the level of evidence supporting each interaction, and recommendations for monitoring. This is one of the most practical tools available for anyone who uses cannabis alongside prescription medications and wants to make informed decisions in partnership with their doctor.
Visit CANN-DIR ToolPatient Education Resources
These organizations and platforms provide trustworthy, ongoing cannabis education for patients and caregivers.
16. Leafly Cannabis 101
Type: Educational Platform
Leafly is one of the largest cannabis information platforms in the world. Their Cannabis 101 section provides well-organized, accessible guides on topics ranging from basic cannabis science to strain selection and consumption methods. While Leafly also operates as a dispensary directory and product marketplace, their educational content is generally well-sourced and useful for beginners. As with any platform that has commercial relationships, readers should be aware of potential conflicts of interest in product-related content.
Visit Leafly Cannabis 10117. Project CBD Beginner's Guide
Type: Nonprofit Educational Organization
Project CBD is a nonprofit organization dedicated to promoting and publicizing research into the medical uses of CBD and other components of the cannabis plant. Their beginner's guide and ongoing reporting translate complex scientific findings into accessible language. Project CBD is particularly strong on the science of cannabinoids and the endocannabinoid system, and they maintain one of the most comprehensive libraries of cannabis research summaries available online.
Visit Project CBD18. Society of Cannabis Clinicians
Type: Professional Medical Organization
The Society of Cannabis Clinicians is a professional organization for physicians and healthcare providers who specialize in cannabinoid medicine. Their website provides educational materials that reflect the perspectives of medical professionals who work directly with cannabis patients. It is a valuable resource for understanding how clinicians approach cannabis therapeutics, and it can help you find healthcare providers in your area who are knowledgeable about medical cannabis.
Visit SCC19. Leaf411 — Cannabis-Trained Registered Nurses
Type: Nonprofit Nurse Hotline
Leaf411 is a nonprofit organization that provides a free hotline staffed by registered nurses who have been specifically trained in cannabis therapeutics. If you have questions about dosing, drug interactions, consumption methods, or how to talk to your doctor about cannabis, Leaf411 provides personalized, evidence-informed guidance from licensed healthcare professionals. This is one of the most underused and valuable resources in the cannabis education space.
Visit Leaf41120. Americans for Safe Access
Type: Patient Advocacy Organization
Americans for Safe Access (ASA) is the largest national member-based organization of patients, medical professionals, scientists, and concerned citizens promoting safe and legal access to cannabis for therapeutic use. ASA provides educational resources on state-by-state legal information, patient rights, and quality standards for cannabis products. They also advocate for policy changes that would expand research opportunities and improve patient access to medical cannabis.
Visit ASA