The most important downside is what’s known as the bell-shaped response curve. Although purified CBD is effective against inflammation and anxiety in rodent and human experiments, its effectiveness peaks at a medium dose but tapers off for higher doses AND lower doses — which graphically looks like an inverted “U” or a bell. Unfortunately, the bell-shaped curve means that purified CBD has limited usefulness — because its effective dose is narrow and difficult to pinpoint.
However, when scientists repeat their experiments with a full-spectrum, CBD-rich extract, the bell-shaped response disappears. In a study involving inflammation in the paws of mice, researchers observed that purified CBD was only anti-inflammatory at a moderate dose, whereas a CBD-rich extract became more effective with a higher dose.