A good antiseizure response to CBD, defined as ≥ 50% reduction in seizure frequency, and an acceptable safety profile have been demonstrated by studies evaluating both children and adults with other forms of TREs [32, 45], such as developmental and epileptic encephalopathy [37, 38, 53], refractory childhood-onset epileptic spasm [34], X-fragile syndrome [54], and SYNGAP1 developmental and epileptic encephalopathy [55]. This evidence concerns the gene SYNGAP1 and fragile X syndrome.