This will be the subject of a Press Complaints Commission complaint. However, I do not expect any satisfaction or proper evaluation of a complaint by the PCC as it has proved itself again and again to be corrupt, dishonest and not in the least concerned with truth, accuracy or enforcing the Editors' Code.
However, I have now spoken directly to Dr Matt Jones, lead author of the study in question and MRC Senior Non-clinical Fellow at the University of Bristol. He told me that he was "disappointed but not surprised" at the Daily Mail's coverage of his work. He gave me permission to quote him in saying that "This study does NOT say that one spliff will bring on schizophrenia".
The Daily Mail, its journalists and its toady apologists on the PCC are liars, cheats and charlatans with not one ounce of integrity, nor any interest in truth or honesty.