For anyone who has these kinds of personality traits in the first place, taking most drugs is only going to exacerbate them and is likely to make them more violent or aggressive. Obviously, all violence isn't a result of drug or substance misuse but I do think it is most of the time. A large majority of violence and aggressive behaviour is caused by drugs like alcohol, crack-cocaine, amphetamine and meth. Additionally, paranoia is largely related to both drug abuse and violence. It's also known that people who suffer with Schizophrenia are more prone to drug addiction whereas the drugs exacerbate their symptoms and when such people become paranoid or get delusional they can react violently, therefore substance misuse is more likely to lead to violence in those cases.