Where cannabis helps—and where the evidence remains uncertain

This article offers a critical overview of the therapeutic role of cannabis and cannabinoids following their recent regulation in Spain through Royal Decree 903/2025 for the use of standardized compounded formulations. In chronic pain, cannabis is not considered a high-potency analgesic, but rather a third-line option for refractory cases, especially neuropathic pain. Its benefit is modest and acts mainly on the affective-emotional dimension of suffering rather than on the nociceptive signal itself. Regarding chemotherapy-induced nausea and vomiting, it is reserved for refractory cases; although it shows benefits compared with placebo, its efficacy is comparable to that of conventional antiemetics and it presents a less favorable toxicity profile. For spasticity in multiple sclerosis, preparations such as nabiximols reduce patients' perception of symptoms, although there is a high discontinuation rate due to lack of efficacy or adverse effects. In contrast, the use of cannabidiol in refractory pediatric epilepsy (Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex) is supported by the strongest evidence. The BECOME study highlights improvements that go beyond seizure reduction, positively impacting alertness, sleep, and family quality of life. Its role in other indications with weak or inconsistent evidence, such as fibromyalgia, glaucoma, anorexia, and anxiety, is also reviewed. In conclusion, although cannabis may offer certain benefits, its integration into modern clinical practice should be cautious, individualized, and carried out under strict clinical supervision. The analysis of real-world use data will undoubtedly provide valuable insights.