Cognition and Long-Term Use of Ganja (Cannabis)
Science July 24, 1981 Jeffrey Schaeffer, Therese Andrysiak, J. Thomas Ungerleider
In ten people who were born, raised, and educated in the United States and had histories of heavy or prolonged cannabis use, cognitive function was not impaired. Urine samples from all ten contained cannabinoid metabolites above 50 nanograms per milliliter, and the cannabis they used had a tetrahydrocannabinol content exceeding 8.0 percent.