Quick summary
- Cannabis has real medical uses, but only for specific conditions, and Thai guidance treats it as an add-on when standard treatment fails, not a first-line drug.
- Six conditions are rated "of benefit," including chemotherapy nausea, hard-to-treat epilepsy and central neuropathic pain.
- There is not enough evidence that cannabis cures cancer.
- Harms are both short- and long-term: dependence, psychosis, road accidents and risks in pregnancy.
- In 2026, legal use in Thailand means medical use under a licensed practitioner only.
- Emergencies: call 1669. Poisoning advice: 1367 (Ramathibodi Poison Center).
Please note: This article is general information, not medical or legal advice, and it gives no dosing. If you have a health condition or take regular medication, talk to a doctor first. Thailand's cannabis law is still being revised and may change.
What does "benefit" mean in medicine?
Online, cannabis is often sold as a cure-all. Thai doctors, however, work from the Department of Medical Services (DMS) Guidance on Medical Use of Cannabis, 6th revision (2024), which sets out clear principles:
- Cannabis products are not recommended as first-line therapy.
- They should be limited to cases where standard treatment has not worked or its side effects cannot be tolerated.
- They are meant to supplement standard care, not replace it.
- Prescribers should be doctors or dentists who have completed a Ministry of Public Health-accredited cannabis course.
In this guidance, "medical cannabis" means plant extracts prepared as products such as sublingual drops, oral sprays or tablets. It does not mean smoking flower. For how THC (psychoactive) differs from CBD (non-addictive), see CBD vs THC explained.
What can cannabis treat? Conditions by level of evidence
The DMS sorts conditions into three groups by evidence quality:
| Evidence level | Example conditions | What it means |
|---|---|---|
| Of benefit (clear, good-quality evidence) | 1) Chemotherapy-induced nausea and vomiting 2) Intractable and drug-resistant epilepsy (e.g. Dravet and Lennox-Gastaut syndromes in children) 3) Spasticity in multiple sclerosis 4) Central neuropathic pain 5) Appetite loss in underweight AIDS patients 6) Quality of life in palliative or end-of-life care | Doctors may consider it when standard care fails, as add-on treatment |
| Probably of benefit (limited good-quality evidence) | Parkinson's disease, Alzheimer's disease, generalised anxiety disorder, other demyelinating diseases | Case-by-case use only when nothing else works, ideally with research-style data collection |
| May benefit in future (insufficient evidence) | Treating cancer itself | Needs more research; cancer patients should receive standard treatment |
Points worth noting:
- Even in the "of benefit" group, the guidance adds limits, for example it does not recommend cannabis for general nausea or for severe morning sickness in pregnancy.
- Epilepsy patients should be managed by a neurologist.
- On cancer, the DMS warns that choosing cannabis alone may cause patients to lose the chance of effective standard treatment.
For prescribed extract products and their legal status, see our guide to medical cannabis extracts and the law.
Short-term risks: common side effects
The DMS explains that adverse effects depend on the amount taken, the user's tolerance and the route of use. THC affects consciousness, attention, short-term memory and judgement. Listed side effects include:
- Brain and mood: euphoria, panic, agitation, mood swings, distorted perception, unsteady walking, slurred speech
- Heart and circulation: fast heart rate, fainting on standing, and in people with risk factors, possible coronary events
- Gut: nausea, vomiting, abdominal pain
- Children: depressed consciousness up to coma, and slowed breathing
- Injury: the guidance flags traffic accidents, falls and self-harm
Driving: Both the DMS and the Ramathibodi Poison Center advise not driving or operating machinery for at least 6 hours after use, and never combining cannabis with alcohol, which further impairs driving. WHO likewise states that acute cannabis intoxication raises the risk of traffic injuries.
Long-term risks: is cannabis addictive, and what about mental health?
Is cannabis addictive? Yes, it can be.
- The DMS notes that sustained high-dose THC causes tolerance, pushing users to take more, and can end in addiction. CBD is not addictive.
- WHO's 2026 technical brief puts the risk of dependence at about 1 in 10 people who ever use cannabis. A review it cites found roughly 12% among young people who had ever used and about 33% among those using at least weekly.
Psychosis: WHO concludes that evidence has strengthened that regular use is a "component cause" that can interact with other factors to trigger schizophrenia or psychotic disorders, with risk rising with frequency and potency of use in adolescence. The DMS similarly explains that people with an underlying mental-health vulnerability may develop psychosis after THC exposure.
Young people: The DMS urges caution when prescribing THC products to anyone under 25 because of effects on the developing brain, and advises against use under 18. WHO links heavy, regular adolescent use with poorer school performance and cognitive impairment, while noting causation is hard to prove.
Smoking: Regular combusted smoking harms the airways; WHO associates long-term smoking with chronic bronchitis.
The picture in Thailand: Thai PBS (July 2024) reported a document from a network of doctors, academics and civil-society groups, citing Ministry of Public Health hospital data, showing outpatient cannabis-induced psychosis cases rising from 6,585 in 2019 to 20,502 in 2023, and outpatients treated for cannabis addiction rising from 16,643 to 32,634. These figures were compiled by that network rather than published as official statistics.
Who should avoid cannabis, and drug interactions
Under DMS guidance, THC-containing products are contraindicated or should be avoided in:
- People allergic to cannabis extract products
- People with unstable heart or vascular disease, or coronary risk factors
- People with a history of psychosis or an active mood or anxiety disorder
- Pregnant or breastfeeding women, or those planning pregnancy, because of reports of preterm birth and low birth weight, and cannabinoids found in breast milk (WHO reports similar associations)
- Extra caution is advised for liver disease, people dependent on other substances or alcohol, users of opioids or sedatives, children and older adults
Drug interactions: THC and CBD are processed by liver CYP450 enzymes and can raise or lower levels of other drugs. The guidance gives examples such as warfarin (a blood thinner) rising to higher levels, the anti-seizure drug clobazam, and drug groups like fluoroquinolones and dihydropyridines. Always tell your doctor or pharmacist about every medicine you take.
Warning signs that need urgent care
The emergency-room screening criteria used in DMS hospitals show which symptoms should not wait:
- Heart: chest pain or tightness, palpitations, irregular pulse, light-headedness, fainting
- Nervous system: confusion, reduced consciousness, seizures, limb weakness, slurred speech
- Breathing: slow breathing, breathlessness, difficulty breathing
- Mind: paranoia, hallucinations, aggression or thoughts of self-harm
- High-risk groups: children, pregnant women, older adults, or people with heart, kidney or brain disease
Who to call
- 1669: emergency medical line run by the National Institute for Emergency Medicine (NIEMS) for critically ill people outside hospital
- 1367: Ramathibodi Poison Center, 24-hour poisoning advice
The Ramathibodi Poison Center also advises keeping packaging and leftovers if someone ate cannabis-laced food unknowingly, and watching for signs of dependence such as using more often, being unable to cut down, or use harming work and family life. If you notice these, see a doctor.
Legal access in 2026: medical use only
- Under the MOPH Announcement on Controlled Herbs (Cannabis) B.E. 2568 (2025), selling flower to an individual requires a prescription from a licensed practitioner treating that patient, limited to a 30-day supply. Online and vending-machine sales and commercial advertising are banned.
- In September 2026 the Cabinet approved a draft Cannabis Control Act, which still has to pass Parliament. The public health minister stressed that cannabis is currently for medical use only, and the draft bans sales to under-20s and pregnant or breastfeeding women.
See how to use cannabis legally in Thailand for the step-by-step process, Thailand cannabis law 2026 for the latest legal overview, and opening a cannabis clinic if you are interested in the provider side.
Bottom line: Cannabis does have benefits for a small set of conditions backed by evidence, but only under medical supervision. Its harms grow with frequency, potency and younger age of first use. The safest step is always to talk to a doctor first.
FAQ
What conditions can cannabis treat in Thailand?
The Department of Medical Services guidance (6th revision, 2024) lists six conditions where cannabis products are of benefit, including chemotherapy-induced nausea and vomiting, hard-to-treat epilepsy, spasticity in multiple sclerosis and central neuropathic pain. In every case it is an add-on when standard treatment has failed, not a first-line therapy.
Can cannabis cure cancer?
There is not enough evidence that cannabis treats cancer itself. Thai guidance places it in the 'may benefit in future' group and warns that relying on cannabis instead of standard care can cost patients their chance of effective treatment. The proven role is limited to easing chemotherapy-related nausea.
Is cannabis addictive?
Yes. WHO estimates that around 1 in 10 people who ever use cannabis develop dependence, with higher risk among young people who use weekly. Thai guidance notes that long-term high-dose THC leads to tolerance and can end in addiction, while CBD itself is not addictive.
What are the side effects of cannabis?
Short-term effects include a racing heart, light-headedness, dizziness, dry mouth, panic, confusion and slower judgement. Longer-term risks include dependence, psychosis and, if smoked, airway problems. Cannabis can also interact with medicines such as warfarin.
Who do I call in Thailand if someone reacts badly to cannabis?
For severe symptoms such as chest pain, collapse, seizures, breathing difficulty or thoughts of self-harm, call the 1669 emergency medical line or go to an emergency room. For poisoning advice, the Ramathibodi Poison Center runs a 24-hour 1367 hotline.
Sources
- Department of Medical Services — Guidance on Medical Use of Cannabis, 6th revision (2024)
- WHO — The health and social effects of nonmedical cannabis use: technical brief (2026)
- Thai PBS — 10 precautions when using cannabis products (Ramathibodi Poison Center)
- Thai PBS — New data on cannabis harms after the pro-cannabis camp claims benefits outweigh harms
- Ramathibodi Poison Center — Contact channels (1367 hotline)
- Government Public Relations Department — NIEMS: what to know before calling 1669
- Thai PBS — MOPH Announcement on Controlled Herbs (Cannabis) B.E. 2568
- Hfocus — Cabinet approves draft Cannabis Control Act; minister says medical use only
