How Can I Tell If Cannabis Studies Are Legitimate?

As cannabis becomes more widely accepted and researched, studies about its effects are appearing at a record pace. Some claim cannabis relieves chronic pain or anxiety, while others warn of cognitive risks or lung damage. It’s no wonder patients are confused. One week, cannabis is a miracle, and the next it’s a menace.

The truth is usually somewhere in the middle. Learning how to evaluate cannabis studies can help you separate facts from hype. Whether you're a patient looking for trusted cannabis information or just want to understand how cannabis research works, it helps to know what makes a study legitimate.

Types of Studies and Why They Matter

The first clue about a study’s credibility is its design. Not all research offers the same level of evidence. Studies fall along a spectrum, from exploratory lab work to rigorous clinical trials.

Meta-analysis

A meta-analysis combines data from multiple studies, using statistics and data analysis to find trends. Through systematic reviews of many different studies, researchers identify patterns, expose inconsistencies, and build the case for (or against) the answer to a clinical question.

For example, in a meta-analysis study in 2015, researchers combined data from 28 studies and found that cannabis-based medicines helped reduce chronic pain in adults.¹ Here, the question or hypothesis “Can cannabis reduce chronic pain?” is assumed to be true, based on many studies.

Clinical Trials

Clinical trials are voluntary human research used to evaluate safety, dosage, or a specific treatment. Randomized controlled trials (RCTs) are the gold standard of clinical research. In these studies, participants are randomly assigned to groups, such as cannabis vs. placebo. 

Reputable clinical trials are often preregistered on sites like ClinicalTrials.gov, where you can check the study design in advance. This helps prevent selective reporting, where researchers only share the most favorable results.

A clinical trial can be interventional or observational. For example, an interventional study may provide cannabis to one group and a placebo to the other, and measure the different results. In an observational study, researchers watch what people are already doing, like using cannabis on their own, and track health outcomes without giving them treatment directly. 

Although cannabis remains federally illegal in the US, newer regulations give researchers some latitude to conduct research and clinical trials. 

In Vitro Studies

In vitro is Latin for “in glass”. Whether in a petri dish or a test tube, these studies are usually on cells or tissue. These studies allow scientists to control their experiments and observe results in a controlled environment.  In vitro studies can provide a foundation for further research on animals, or eventually, human subjects. 

A breakthrough in vitro study in 2007 allowed scientists to determine in lab tests using human breast cancer cells that CBD slowed the growth of the cells and helped cause cell death.²

Animal Studies

Animal studies allow researchers to gain knowledge and determine if a drug or treatment is safe and effective before human testing. In cannabis research, a study conducted on mice found that CBD helped reduce anxiety and fear responses after stressful experiences.³

Other Study Considerations

Beyond the type of study, there are other areas to consider when evaluating cannabis research. 

Sample Size and Study Population

Even a well-designed study may not be significant if it includes only a small number of people. A study involving ten patients might suggest an interesting trend, but a study involving 1,000 is much more reliable.

Large, diverse sample sizes increase the credibility of a study’s conclusions. Researchers should also clearly explain the criteria for including subjects and why. For instance, a study testing cannabis on only college-aged males may not apply to older adults with chronic pain. Studies should define their inclusion and exclusion criteria, so readers know how representative the data is.⁴

Researchers also use statistical methods to determine whether a result is significant or could have happened by chance. But even with strong statistics, a small sample can overstate an effect, or miss important patterns entirely.⁵

Funding and Conflicts of Interest

Before trusting a study’s conclusion, consider: Who paid for this research, and do they benefit from the outcome? This isn’t always a deal breaker. Companies, governments, or advocacy groups fund many valid studies. But transparency is key.

A legitimate study will clearly state its funding sources and disclose any conflicts of interest. If a cannabis company or pharmaceutical firm employs researchers, that doesn’t mean their results are invalid, but results may be more likely to favor their product.

Historically, U.S. government-funded cannabis research has focused more on potential harms than benefits, due to longstanding legal and political barriers. While this is slowly changing, it’s important to understand the goals and limitations of each funding source.⁶

Confounding Variables: The Hidden Biases

One of the biggest challenges in all research is controlling for confounding variables. These are factors that may influence outcomes without being part of the study’s focus. For example, a study linking cannabis use to depression might not account for past trauma, economic hardship, or other significant events.

The best studies try to rule out outside factors that could affect the results, either by how they set up the research or by using math to adjust for them. 

 If a study doesn’t explain how it handled these outside influences, it’s a good idea to read it more carefully.⁴

Researchers often use frameworks like the Cochrane Risk of Bias tool or the GRADE system to measure the reliability of studies. Readers don’t need to know all the details, but recognizing that these tools exist shows a study was held to a high standard.

Do the Results Really Back Up the Claims?

Sometimes researchers draw bigger conclusions than their data justifies. A study might show a minor correlation, but the abstract or media coverage suggests a “major” breakthrough.

When reading cannabis studies, check whether:

• The results are statistically significant 
• The authors acknowledge limitations
• The conclusions match the evidence presented
  

Overreaching or ignoring limitations is a red flag. Ironically, the most trustworthy studies often sound careful or unsure, since good scientists are honest about what they can or can’t prove.

It’s also worth remembering that studies with positive or striking results are more likely to be published than those with neutral outcomes. This is a problem known as publication bias. That’s why replication across many independent studies is so important.

Replication 

In science, one study doesn’t make a fact. Look for results replicated by other studies by independent researchers, in different settings, and with various populations.

Reproducibility, or getting consistent results across multiple studies, is a positive indication of reliability. If a study goes against most of the earlier research or lacks support from other studies, consider it a starting point and not a final answer until more evidence is available.⁵ 

Publication Source and Corroboration

It does matter where a study is published. Reputable, peer-reviewed journals have strict standards for methodology, data transparency, and ethics. Peer-reviewed means that other scientists in cannabis medicine evaluate and provide feedback and recommendations to the authors before publication. This process fact-checks the structure and data presented in the report and improves the overall quality of published research. 

You can search for studies in databases like PubMed Central or ScienceDirect. Be wary of so-called “predatory journals,” which publish articles for a fee with little to no peer review. If a study appears in a journal you’ve never heard of, do a quick background check.

For patients evaluating new cannabis research, it may also help to consult a medical provider or seek insights from trusted sources of cannabis.

Are Newer Studies Better Than Older Ones?

Not always. It’s true that some older cannabis studies created during a time of strong stigma and bias against cannabis might not meet today’s research standards. But newer studies aren’t always better. Some are still small, biased, or poorly designed. Other new studies may use technologies that are difficult to replicate. What matters is the quality of the study, not how old it is. That said, newer research often relates more directly to the cannabis products, ways of using them, and medical needs we see today.

Get Another Opinion

Understanding how to spot good research doesn’t require a science degree. But before you depend on the conclusion of any medical cannabis study, it’s worth getting a second opinion.

Patients can talk to a medical marijuana doctor about what the research means for their specific needs, and by preparing with thoughtful questions. 

Trusted sites like NuggMD have reviewers who hold professional degrees in cannabis or are doctors, pharmacists, nurse practitioners, or other professionals who verify the information presented. The best sources of cannabis information also cite peer-reviewed journals to back up their claims.

1. Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for Medical Use. JAMA. 2015;313(24):2456. doi:https://doi.org/10.1001/jama.2015.6358 ↩︎
2. McAllister SD, Christian RT, Horowitz MP, Garcia A, Desprez PY. Cannabidiol as a novel inhibitor of Id-1 gene expression in aggressive breast cancer cells. Molecular cancer therapeutics. 2007;6(11):2921-2927. doi:https://doi.org/10.1158/1535-7163.MCT-07-0371 ↩︎
3. Campos AC, Ortega Z, Palazuelos J, et al. The anxiolytic effect of cannabidiol on chronically stressed mice depends on hippocampal neurogenesis: involvement of the endocannabinoid system. International Journal of Neuropsychopharmacology. 2013;16(6):1407-1419. doi:https://doi.org/10.1017/s1461145712001502 ↩︎
4. MGH Guides: NH-720 Research for Clinical Practice: Evaluating Research Articles. Massgeneral.org. Published 2017. Accessed August 1, 2025. https://libguides.massgeneral.org/c.php?g=650977&p=10796411 ↩︎
5. Wilkinson D. Research quality – not all research is good research, but how do you tell? The Oxford Review. Published November 8, 2019. https://oxford-review.com/research-quality/ ↩︎
6. Bekelman JE, Li Y, Gross CP. Scope and Impact of Financial Conflicts of Interest in Biomedical Research. JAMA. 2003;289(4):454. doi:https://doi.org/10.1001/jama.289.4.454 ↩︎

The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.