A study conducted at the University of Freiburg, Germany provides deep insight on this subject. The study was solely centered on finding out if it’s possible to fail a drug test by touching cannabis. 10 participants in the study were asked to roll a joint a day and these participants were subjected to drug tests every day. The results from the tests showed that by the middle of the study, most of the participants showed good levels of THCA and THC in their systems. Four weeks after the study, hair samples of 5 participants still showed levels of THC in their system.