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Medical use of cannabis

Understanding whether a cannabis-based product has a place in your care, or reviewing use that has already started. No cure-all, no embellishment.

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Five hand-painted wooden matryoshka dolls from João’s office

The plain truth is that good-quality scientific evidence for medical cannabis is still limited for many of the conditions people seek it for. That does not end the conversation. It can be considered with transparency, reliable information and close follow-up, without turning a possibility into a promise.

The question usually comes from patients themselves. It is worth exploring what lies behind it: what has not improved, which treatments caused problems and what you hope to find. Often, that conversation opens other paths that might make sense before or alongside cannabis use.

When evidence is weak, a decision needs greater care. The person’s preference matters, as do the clinical context, available alternatives and the balance of risks and possible benefits. Consent alone does not make every prescription appropriate.

What the evidence allows us to say

Medical cannabis includes products with different compositions. A result found for one product and condition does not automatically apply to another oil or another illness. Doses and responses also vary between people.

There is stronger evidence for a specific CBD formulation in treating seizures associated with certain epilepsies, such as Dravet syndrome, Lennox-Gastaut syndrome and tuberous sclerosis. For chronic pain, some THC-containing products have shown short-term benefit, mainly in studies of neuropathic pain, but also increased dizziness and drowsiness. Important uncertainties remain about long-term use.

For other concerns, such as anxiety, insomnia and fibromyalgia, findings are more preliminary or conflicting. Many patients report meaningful changes in sleep, symptoms and quality of life. Those accounts deserve attention and follow-up, even though they cannot establish that the product will have the same effect for someone else.

With these uncertainties, it makes a difference to have a professional whose clinical knowledge extends beyond cannabis. Care needs to address the problem that brought you to the appointment, other possible treatments and what is happening in your life. It cannot be reduced to prescribing a medicine.

Before prescribing

The assessment includes current medicines and supplements, previous treatments and your health history. It is important to understand interactions, individual risks and alternatives with more established evidence for your situation.

CBD and THC have different effects, and the ratio between them matters. Even CBD products can cause side effects and interactions. Alcohol, drowsiness, driving safety and a possible need to monitor the liver belong in the conversation, depending on the product and your history.

Follow-up is part of prescribing

A trial needs clear goals: what is expected to improve, how to observe that change and when to discuss it again. At follow-up appointments, benefit, unwanted effects and the impact on everyday life help decide whether to continue, adjust or stop treatment.

Responsible prescribing includes acknowledging uncertainty and being available to reconsider the approach. My aim is for that conversation to be honest, without automatic enthusiasm or dismissing from the outset a possibility that could make sense for you.

Questions before your visit

Do CBD and THC have the same effects?

No. THC can change perception, attention and mood, with effects ranging from euphoria or relaxation to anxiety and paranoia. Choosing the product and gradually adjusting the dose aim to find benefit with fewer unwanted effects, without eliminating all risks. CBD does not produce the same intoxication, but can cause drowsiness, interact with medicines and affect the liver. A CBD product may also contain THC; its composition needs checking.

Do I need to stop my other medicines?

Do not stop anything on your own. The assessment includes interactions and whether each treatment should continue or change. If there is improvement, it may make sense to reassess other medicines. Evidence for using cannabis to help stop benzodiazepines, such as clonazepam, remains limited. Deprescribing needs an indication, caution and a plan of its own; it is not an automatic consequence of starting cannabis.

What should I bring if I already use a product?

Bring the packaging or clear photos of the label and ingredients, your prescription if you have one, and a list of medicines and supplements. Make a note of how you use it, what changed in your symptoms and whether you noticed any unwanted effects.

Which medicines need particular attention?

Examples include clobazam, valproate, warfarin and tacrolimus. Interactions and precautions vary with the product, dose and other treatments. Drowsiness, blood pressure and fall risk also deserve attention. This is not a complete list: it is important to bring all medicines and supplements to the appointment.

What patients say

Reviews published by patients on Doctoralia and Google. Original wording and language preserved.