9. Marijuana use slightly reduces the risk of being involved in a car crash.
Studies reported in the online document Marijuana Use: Detrimental to Youth by the American College of Pediatricians indicate that marijuana use at least doubles the risk of involvement in an accident. In addition, accident risk from even low levels of marijuana and alcohol combined are greater than either substance separately. Link: (Marijuana Use Detrimental to Youth)
These findings are corroborated by simulation driving studies that have shown a direct relationship between THC concentration and impaired driving ability. Link: (Does Marijuana Use Affect Driving)