It may have something to do with the fact that THC stimulates that CB1 receptor a lot, in turn triggering the psychoactive effects of marijuana like disturbed sensory perception, impaired motor skills, and anxiety. Conversely, CBD stimulates CB1 very lightly, causing some effects that seem downright opposed to those of THC including relief from anxiety, stress, and hyper-excitability.
One of the strongest nutraceutical CBD oils is called Charlotte’s Web, with a 50mg dose. Charlotte’s Web is produced in Colorado by the Stanley Brothers, and named after Charlotte Figi, a girl who became famous in the US after her frequent seizures, brought on by the rare Dravet syndrome, were greatly reduced when she started taking CBD oil aged five. The company makes THC products too and is extremely successful, having just offered shares on the Canadian securities exchange, raising about $100m.