Cannabis Impairment Detection: The Ultimate Guide

Cannabis Impairment Detection: The Ultimate Guide

New Mexico Expands Employment Protections for Medical Marijuana UsersIt’s no secret that cannabis impairs driving ability. That much is clear. But the effects of cannabis on a person’s reaction time, vision, and other senses vary depending on how much THC is present in their blood. Consequently, drivers can adversely react to road and traffic conditions when they are under the influence of cannabis, which puts them and everyone else on the road at risk of injury or death. In order to decrease the number of drivers who operate vehicles while impaired by THC, the need for a reliable detection system has become imperative. This article will explore topics relating to cannabis impairment detection with respect to active THC levels in drivers and inactive CBD levels in drivers as well as methods for detecting these active cannabinoids as they relate to safe driving practices.


What Is THC and What Does It Do?


THC is the abbreviation for tetrahydrocannabinol, one of the active cannabinoids (chemical compounds) found in the Cannabis plant. It is responsible for the “high” feeling associated with cannabis consumption. Common side effects of THC intake include impaired motor skills, altered senses, anxiety, paranoia, and an increased heart rate. These side effects vary depending on the amount of THC present in a person’s system. As THC builds up in the system, the effects last longer and become more intense. The extent of impairment caused by THC varies from person to person, and from time to time. Factors such as genetics, diet, and physical fitness can have a significant impact on how THC affects a person.


How Long Does THC Stay in Your System?


In most cases, THC metabolites are detectable in the human system for up to 50 hours after consumption. This means that the active cannabinoids present in cannabis can be detected in a person’s system for almost two days after smoking or ingesting (eating) cannabis. It is important to note, however, that there are significant variations in this estimation based on the individual and other factors. For instance, frequent and/or heavy cannabis users have a higher THC level in their systems than first-time users. This is why frequent and/or heavy cannabis users are more likely to test positive for THC in a cannabis impairment testing situation.


Safer Ways to Determine Cannabis Impairment


  • Blood/Blood Plasma Samples: One of the most accurate ways to determine cannabis impairment is through a blood sample. A blood sample can determine the precise amount of active THC in a person’s system and can be used to assess whether the driver was impaired. 
  • Urine Tests: These are less accurate than blood samples because THC metabolites stay in the system longer. However, they are less invasive and are therefore used more often. 
  • Hair Follicle Tests: These are also less accurate than blood and urine tests. They can also be difficult to interpret accurately, because every individual grows hair at a different rate. 
  • Field Sobriety Test: This test is often used by police officers to determine whether someone is impaired while driving. It is not a very accurate way of determining THC levels, but it can be helpful in combination with other tests.


The need for a reliable impairment detection system is more crucial than ever as the number of people who use cannabis increases. If you’re ever in a situation where you have to be tested for cannabis impairment, be sure to know what is being tested for and what your options are when it comes to defending yourself against the accusation.