A single “it cured me” story is one of the weakest kinds of medical evidence, even when the person writing it is honest. This part shows which study designs can actually test a treatment claim and how the evidence grades in a major 2017 review work. It also covers what patient stories are genuinely good for and gives you a checklist for reading a recovery post.
Part 1 explained the eight filters between a real recovery and the story you read. Only the people who recovered write. There is nothing to compare with. Placebo can be large. Other treatment was often happening at the same time. Illness changes by itself. Follow-up is missing, the diagnosis cannot be checked, and everyone in the chain sees what they expect. This part explains what can get past those filters.
This is Part 2. Part 1: Why Personal Testimony Is Not Medical Evidence — and What It Is Good For Instead
4. What each kind of study can and cannot rule out
Each type of study is built to rule out some of the filters from Part 1, and none rules out all of them. A few terms first:
- Case report: A doctor’s published description of one patient, with the diagnosis confirmed and the course of the illness recorded.
- Case series: Several patients with the same condition, all described in the same way.
- Observational cohort: A study that follows groups of people who chose different treatments themselves, then compares how they did.
- Confounding: The groups differ in ways other than the treatment, and those differences affect the result. In farming terms, the plots that got the new fertiliser might also be the ones with the better soil.
- Randomised controlled trial: Participants are assigned to treatment or comparison by chance, like drawing lots. This makes the groups similar on average. Farmers who run field trials with randomly placed plots use the same idea.
- Blinding: Nobody knows who got the real product, so expectation cannot tilt the result.
- Publication bias: Studies with positive results are more likely to be published than studies that found nothing.
| Design | What it rules out | What it still cannot rule out |
|---|---|---|
| Personal story (testimonial) | Nothing | All eight filters in Part 1 |
| Published case report | Diagnosis is confirmed and the course is recorded | Chance, other treatment at the same time, which cases got published |
| Case series | Several patients described in a consistent way | No comparison group; which cases got included |
| Observational cohort | Has a comparison group and larger numbers | Confounding: the groups differ in more than the treatment |
| Randomised controlled trial | Confounding, through allocation by chance | Blinding that fails; small trials can still mislead |
| Blinded, placebo-controlled randomised trial | Confounding and expectation | Publication bias; results may not apply to everyone |
| Systematic review / meta-analysis | Flukes from a single study and selective reporting | It is only as good as the trials it combines |
The table does not say personal stories are worthless. It says they sit in the top row, the weakest design. Medicines are approved on the strength of the rows at the bottom.
What to do: When a post or product says “research shows”, find out which row of this table that research belongs to. That tells you how much weight the claim can carry.
5. Evidence grades: how a major 2017 review rated cannabis claims
In 2017, the US National Academies of Sciences, Engineering, and Medicine (NASEM), an independent scientific advisory body, published a large review of the evidence on cannabis and health, The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Instead of a yes-or-no answer for each condition, it gave every conclusion one of five grades:
- Conclusive evidence: Many good-quality studies agree, and there is no credible opposing evidence.
- Substantial evidence: Strong support from several good studies, with only minor doubts.
- Moderate evidence: Some good studies support it, but there is real uncertainty.
- Limited evidence: Weak or mixed support, with major doubts.
- No or insufficient evidence: There are not enough good studies to say anything.
The grade describes how firm the evidence is. It does not describe how large the effect is. Some examples of how NASEM graded common claims:
- Chronic pain in adults: substantial evidence that cannabis is an effective treatment.
- Nausea and vomiting from chemotherapy, with oral cannabinoid medicines: conclusive evidence.
- Muscle stiffness in multiple sclerosis, as reported by patients: substantial evidence for oral cannabinoids.
- Treating cancers themselves, including the brain tumour glioma: no or insufficient evidence.
Grades describe the evidence as it stood when the review was written. Later work can change the picture. For example, the 2022 Gedin review covered in Part 1 pooled 20 blinded pain trials with 1,459 participants. Placebo also reduced pain substantially in those trials. The gap between the real product and placebo was not statistically significant. No number of personal stories can move a grade up or down, because stories sit in the weakest row of the table in section 4.
What the grades give you: a quick way to tell how firm a claim is before you spend money or change a treatment. How to use them in Thailand: when a seller, a post or a relative says “studies prove it”, compare the claim with the grade for that condition. Then take the question to your doctor. Where to start: look up only the one condition you care about in the NASEM conclusions (the full report is free to read online: The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research | The National Academies Press), and note its grade.
What to do: Write the condition and its grade next to any claim you are weighing. A “cure” claim for a condition graded “no or insufficient evidence” should make you stop and ask your doctor.
6. What patient stories are genuinely good for
Dismissing patient reports completely is also a mistake, and it can be a costly one. Stories have four real uses.
Pointing to what is worth testing. Patient reports are often the first sign that something deserves a proper study, and they have led to formal studies many times. A cannabis example comes from Dravet syndrome, a severe epilepsy that starts in childhood. Before cannabidiol (CBD, a non-intoxicating cannabis compound) was tested in randomised trials for this condition, there were widely publicised family reports. A 2013 survey of parents also described dramatic drops in seizures.
The double-blind, placebo-controlled trial that followed was published by Devinsky and colleagues in the New England Journal of Medicine in 2017. It included 120 patients. It confirmed that cannabidiol reduced convulsive seizures more than placebo. However, becoming completely seizure-free was rare: 5% with cannabidiol versus 0% with placebo, a difference that was not statistically significant. That is far less than the most striking reports had suggested. The right response to a striking report is a study, not a conclusion. The report earns the study, and the study then measures how large the effect really is.
Catching side effects. Here patient reports are essential, not just useful. Rare harms usually show up after a medicine is approved, when far more people use it than any trial included. Drug safety monitoring systems (pharmacovigilance) exist to collect exactly these reports. A patient who describes an unexpected reaction is contributing solid data.
Translator’s note: In Thailand, if you have an unexpected reaction to a cannabis product, tell the practitioner who prescribed it or the pharmacist who dispensed it. They can forward it to the Health Product Vigilance Center (HPVC) of the Thai Food and Drug Administration, which collects reports of side effects of health products. You can also report it yourself on the HPVC website (hpvcthai.fda.moph.go.th). Licensed shop operators can find how to keep an adverse-event log in this topic on running a dispensary.
Describing what living with a treatment is like. Trials measure set outcomes. They rarely show whether a medicine is bearable to take every day for ten years or whether it gets in the way of work. They also rarely show which side effect actually makes people stop.
Showing where health care is failing. Sometimes many patients say they found cannabis themselves because no doctor would discuss it with them. That is a real finding about a health system. It holds true whether or not the treatment works.
What to do: If you post your own experience, include any side effects, how long you have used the product, and what else you take. Those details turn a story into something other people can actually use.
7. A checklist for reading a recovery post
| Question to ask | What a stronger account includes |
|---|---|
| What was the diagnosis, and how was it confirmed? | The named condition, its stage, and how a doctor established it |
| What other treatment was the person getting at the same time? | A full treatment list, including standard medical treatment |
| How long is the follow-up? | Years, with updates, not weeks |
| Who else took it and did not improve? | Any sign that the writer knows other people tried it too |
| Was anything measured, or only felt? | Scans, lab results, standard symptom scores |
| Who put this collection together, and what do they gain? | No link to anyone selling a product |
| Does the same story pattern appear for unrelated diseases? | If yes, the pattern comes from the person who wrote or collected the stories, not from the disease |
What to do: Copy these seven questions into your notes or phone. Run any recovery story through them before you share it or act on it. Each “no answer” shows a gap the story cannot fill.
8. If you are the person with the diagnosis
None of this is a reason to doubt your own experience or to keep quiet about it. It is a reason not to let a stranger’s story decide your treatment. Keep three things in mind.
- Relief of symptoms and treating the disease are separate questions. Evidence for the first is not evidence for the second. A cannabis product may truly help you eat, sleep or feel less sick without changing the illness itself.
- Your treatment team needs to know everything you take. One reason is interactions between medicines (see the drug interaction list to take to your doctor). The other is that your doctors cannot read your test results correctly without it.
- Declining or delaying a treatment known to improve survival is the highest-stakes decision you can make. The article on declining cancer treatment in favour of cannabis sets out what is known about the outcomes of that choice.
Translator’s note: In Thailand, bring every product you use to your hospital appointment, including oils you got from friends or that have no label. Cannabis flower can only be obtained lawfully with a PT 33 prescription covering at most 30 days. Asking your treating doctor about it is therefore also the lawful route. Some Thai public hospitals run medical cannabis clinics, so ask your doctor whether your hospital has one. Dosing guidance is covered in Start Low, Go Slow.
Join the discussion: If you have read a recovery story that you found genuinely convincing, post it in the replies. We can go through it together using the checklist in section 7. The aim is not to win an argument. Working through one real example teaches the skill better than any checklist on its own. If you have a story that did not end the way you hoped, please consider sharing it as well. That kind of account is worth more to this community than the successful ones, and it is harder to post.
Related topics:
- Rick Simpson Oil: the history of the cannabis-oil cure claims
- Cannabis and Cancer: what the evidence supports and what it does not (also linked in Filter 4 of Part 1)
- Start Low, Go Slow: published guidance on medical cannabis dosing (linked in section 8)
- Declining cancer treatment in favour of cannabis, Part 1 (linked in section 8) and Part 2: children, online advice and who carries the legal risk
References
- Gedin F, Blomé S, Pontén M, Lalouni M, Fust J, Raquette A, Vadenmark Lundquist V, Thompson WH, Jensen K. Placebo Response and Media Attention in Randomized Clinical Trials Assessing Cannabis-Based Therapies for Pain: A Systematic Review and Meta-analysis. JAMA Netw Open. 2022;5(11):e2243848. doi:10.1001/jamanetworkopen.2022.43848
- Ellison GL, Helzlsouer KJ, Rosenfield SM, et al. Perceptions, prevalence, and patterns of cannabis use among cancer patients treated at 12 NCI-Designated Cancer Centers. J Natl Cancer Inst Monogr. 2024;2024(66):202–217. doi:10.1093/jncimonographs/lgae029
- Devinsky O, et al. Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. N Engl J Med. 2017;376(21):2011–2020. doi:10.1056/NEJMoa1611618
- Koubeissi M. Anticonvulsant Effects of Cannabidiol in Dravet Syndrome. Epilepsy Curr. 2017;17(5):281–282.
- National Academies of Sciences, Engineering, and Medicine. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington, DC: The National Academies Press; 2017. doi:10.17226/24625
This article belongs to the Asiannabis Community educational series on judging medical claims. It is general information, not medical advice. If you face a treatment decision, the people who can help you make it are the clinicians who know your case.