“CBD inhibits the cytochrome P450 enzymes that break down important psychiatric drugs,” says Blessing. CBD isn’t the only substance that messes with the body’s ability to metabolize these drugs — both St. John’s wort and the humble grapefruit are unfriendly — but CBD is comparatively poorly studied. The way CBD inhibits those enzymes could dramatically raise the levels of SSRIs or opioids in the system, potentially leading to an overdose.
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.