The Columbian, 10 Oct 2012 – I would like to briefly describe the three studies Ann Donnelly mentions in her Oct. 3 letter "Recognize high risk of marijuana." First, the research linking tetrahydrocannabinol to schizophrenia is based on findings from administering volunteers with large doses of pure THC intravenously. Indeed, symptoms mirroring schizophrenia occur under such circumstances, but nobody is going to be injecting themselves with incredibly large doses of pure THC.