The presence of marijuana can be verified from a number of tests, one of them being the hair test. It is considered to be one of the most objectionable form of drug test. The difference with drug hair test is that it does not try to detect if one has recently used marijuana recently. It looks for the non psychoactive residue left behind in the hair months after the consumption. Residue is absorbed into the system and will not present on the hair until after seven to ten days after initial use. This is so permanent that it cannot even be washed off using shampoos, what shampoos achieve is the removal of smoke particles that may have stuck on the hair.
To determine marijuana use on the hair, results can be more conclusive for regular users but the case may not be for those who are occasional users. In a research study it was found that 85 percent of regular users, results came back positive for cannabis presence against a 52 per cent presence for irregular users which translates to one to five times each week. When cannabis is eaten it will be less likely for it to be detected when compared to inhaled marijuana. It is not very clear if hair tests can detect marijuana use for one time users of the drug.
With all things being constant, it will take at least five days for cannabis to present in the hair. This being said its presence will continue to be seen in the hair for several months to come. Marijuana presence or the presence of any other drug for that matter in the hair should be understood from this one principle.
When marijuana is consumed, it is digested by the body system, where it finds its way into the bloodstream, saliva, urine and also into the hair through the blood. Marijuana presence in the hair will be found in the hair follicles. Marijuana metabolites, THC-COOH, which is deposited in the follicles, are enclosed in the hair shaft as it prepares to emerge from the hair follicle. Let us assume that the average hair growth rate as approximately 0.5 inches every month across board.
Laboratories that conduct marijuana drug tests test for the cannabis metabolites normally found trapped in the hair shaft core. Any previous drug use will be found based on the hair length that will be taken as a sample from your hair line however a specific amount of timeline from which their hair can be used cannot be determined. The test will not be able to distinguish between THC metabolites that came into the hair two weeks prior to any metabolites that are present in the hair from the consumption done two days ago.
As an example let us take a hair sample of 1.5” length when measured from the root. Depending on the hair growth rate of the previous assumed figure of 0.5 inches monthly, a positive result would go with the assumption that cannabis was used within the last three months.