ARTICLES
The adverse effects of Cannabis and the challenge of verifying impairment
Cannabis is one of the most widely used recreational drugs in the world. Tetrahydrocannabinol (THC), the psychoactive principal constituent of marijuana (Cannabis sativa), is present in the plant, at concentrations of up to 12% by weight. It is taken either orally or by smoking, resulting in sedation, euphoria, hallucinations, time-space distortions, fear, distrust and a profound state of unease.
Long-term use can result in respiratory and cardiovascular toxicity and has been implicated in a range of long-term psychiatric illnesses. Driving under the influence of THC is associated with approximately double the risk of motor vehicle crashes.
Following acute use, THC only remains in the blood for several hours before it is converted into to a carboxylic derivative of THC and this partitions into the fat from where it leaches out in a form that can be detected in urine for weeks after use.
However although this may indicate recent use of cannabis, it is unable to establish whether a person was intoxicated or impaired at the time the sample was obtained. Testing for impairment requires blood or saliva to be tested.
