There is absolutely no reliable scientific evidence that THC is necessary to synergize the effects of CBD. Instead, there is evidence from preclinical research that THC may be pro-convulsant in sensitive brains; other research indicates that chronic use of THC can impair IQ in adolescents. Physicians are beginning to report instances of THC toxicity in children taking “high CBD” preparations, e.g., high anxiety, increased seizures, insomnia, etc. Until more is known, the most conservative course of action would be to remove THC entirely from a CBD product.