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Results: Fifty studies were included in this systematic review. A total of 4791 participants were collected. ... Subgroup analyses showed that there was no significant difference on efficacy and safety among age subgroups and epilepsy syndromes subgroups. For most periods, there were no significant difference on efficacy among subgroups of dose and concomitant ASMs. However, higher doses and more concomitant ASMs were associated with higher proportion of adverse events.
Conclusion: Cannabidiol treatment of DRE has stable efficacy and fewer adverse events in early period. Long-term use may have decreased efficacy and increased adverse events. Dose escalation may not increase efficacy, but may increase adverse events. Furthermore, cannabidiol use may reduce dosage of other ASMs without reducing efficacy, thereby reducing adverse effects. Cannabidiol may have similar effects in various epilepsy syndromes.

Long-term efficacy and adverse effects of cannabidiol in adjuvant treatment of drug-resistant epilepsy: a systematic review and meta-analysis - PubMed
PROSPERO (CRD42022351250).

Commercially available CBD oils can vary wildly in quality, but I would have to think that folks participating in studies would be using a CBD oil with higher quality control and standardized formulations. The conclusion seems to indicate that CBD oil is not a good long term option.
