"Drug testing of any kind, including for cause or suspicion, was not a significant predictor of marijuana use. These results remained for all samples, even after controlling for student demographic characteristics."
Source
Yamaguchi, Ryoko, Lloyd D. Johnston & Patrick M. O'Malley, "Relationship Between Student Illicit Drug Use and School Drug-Testing Policies," Journal of School Health, April 2003, Vol. 73, No. 4, p. 163.
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