Yeah, it's a depressant.
Alchohol makes people aggressive because it's a stimulant, contrary to popular belief.
Heroin would be a LOT safer if it were legalised, in a controlled manner. Street heroin contains a lot of poisonous additives etc. which would be eradicated, taking the drug in a controlled environment also takes the risks of overdoses away, as shown in so called "shooting galleries" (in holland I think), where all the drugs-related problems in the virtually vanished. The government would also be able to help people addicted to the drug, as they would have better contact with the users, helping them to get off it, and controlling it financially. Of course though, the government is far to scared to even try any of this out.