Fact: The rate of pot use is higher among offenders than nonoffenders, but that definitely does not mean that pot causes criminal behavior. Another factor may be driving both results – or it could be that the causality goes the other way, and criminals are just more likely to use drugs. Furthermore, pot, unlike alcohol, doesn't generally unleash aggression, so it's much harder to link it to violent crime.

Source: Marijuana Legalization: What Everyone Needs to Know