A 1999 study by the National Academy of Sciences concluded that, "Few marijuana users develop dependence." Some do, "but they appear to be less likely to do so than users of other drugs (including alcohol and nicotine) and marijuana dependence appears to be less severe than dependence on other drugs."
A 2005 study led by Dr. Carl Soderstrom at the University of Maryland School of Medicine concluded that drivers who test positive for marijuana in urine are no more likely to cause accidents than drug-free drivers.
Similarly, a 2002 review of seven separate studies involving 7,934 drivers reported that, "Crash culpability studies have failed to demonstrate that drivers with cannabinoids in the blood are significantly more likely than drug-free drivers to be culpable in road crashes."
The truth is: the most significant danger associated with marijuana use is the federal government's 70-year-old war on the Cannibis plant.