Testing For Marijuana: Is It Effective?

Yes and no. Marijuana impairment can be detected through visible signs and confirmed by a biological test; however, the more useful metric of functional impairment cannot be reliably measured.

Visible signs of marijuana impairment include: fatigue, impaired memory and concentration, general disorientation, spontaneous laughter, dilated pupils, bloodshot eyes, nervousness, impaired motor skills, dry mouth, coughing, nausea, and increased appetite.^1,2 But these are common symptoms with multiple possible causes and therefore cannot be relied upon as definitive proof of marijuana impairment.

Biological testing is the only way to confirm the presence of tetrahydrocannabinol, or THC – the primary psychoactive compound in marijuana – in an individual's body. Saliva and blood tests are the most accurate testing options and saliva is the best at indicating recent use.^3,4 Unfortunately, THC remains in the body anywhere from four days to two months after last use,⁵ while