THC – or delta-9-tetrahydrocannabinol (THC), the most researched cannabinoid – is responsible for the way your brain and body respond to cannabis, including the high and intoxication. THC has some therapeutic effects but it also has harmful effects. Harmful effects may be greater when the strength of THC is higher.
The potency (concentration or strength) of THC in cannabis is often shown as a percentage of THC by weight (or by volume of an oil). THC potency in dried cannabis has increased from an average of 3% in the 1980s to around 15% today. Some strains can have an average as high as 30% THC.