Can I give CBD to a 14-year-old with involuntary movements?

Although involuntary movements don't quite classify as epilepsy, there is research on the effect of CBD products on adolescents who suffer from epilepsy. This study, in particular, contained children younger even than 10. What they found was that the majority of the patients experienced a reduction in the frequency of their seizures, some stopping entirely.

The study was not without adverse reactions, however. Around 25% of the patients experienced beneficial reactions to their mood, sleep patterns, and spasticity of their movements, while around 50% experienced feelings of drowsiness. What's good to note about this is that all the patients who did experience adverse reactions were able to reverse them in as short as 24 hours after stopping the treatment plan.

It's also important to note that this study used a CBD:THC ratio of 20:1, and THC is widely known as the reason for most adverse reactions caused by cannabis. The CBD products you can buy in stores contain far less THC as required by law.

The short answer to your question is that you can't really know if your child will experience any bad effects or not until you try. If you're determined to use CBD products, start small (around 5mg/day) and monitor him closely, increasing the dose by 5mg/week until you notice a change. And even though your doctor won't prescribe you CBD products, you're still allowed to ask for his advice and opinion.