This is a tricky question. An overdose from weed is almost medically impossible, at least from the directly ingested active ingredients. But what we don't have quantified and never will is how many people have died more indirectly but still from a cannabis-triggered event. Pathologists in every community will assure you they see those deaths very regularly. Visit a coroner and ask. These are the people who smoke too much weed, often in combination with other medical problems, and suffer a deadly arrhythmia or throw an embolism or have an aneurysm that breaks open and floods the brain or a fit of coughing that results in pulmonary failure. A lot of folks will argue that those are then the result of other medical problems, which is only partially true. Had they not toked up in their already weakened conditions, they might have lived lots longer. There are hundreds, if not thousands, of those deaths every year. But still people like to keep perpetuating the no-deaths-at-all angle.