Medical cannabis that contains THC also known as tetrahydrocannabinol is used to treat a wide variety of conditions. The amount of THC used to treat medical illness is much lower than that taken by recreational users. THC used in combination with CBD (cannabidiol) is considered the effective treatment for a range of conditions. CBD combined with THC may potentially counteract some of the side-effects. THC is the know psycho-active chemical found in cannabis. Low levels of THC used to treat medical illness are not expected to cause a feeling of being ‘stoned’ or ‘high’.